Publications

organochlorine residues and eggshell measurements for tree swallows tachycineta bicolor in colorado.		1985	3935192
mutual restraint in tree swallows: a test of the tit for tat model of reciprocity.	the tit for tat model of reciprocity, which is based on a successful program for the game known as the prisoner's dilemma, was experimentally tested on a population oftree swallows (tachycineta bicolor). parent and nonbreeding tree swallows have conflicts of interests that resemble those in the prisoner's dilemma. tit for tat predicts restraint of conflict before a competitor's act of defection, retaliation after defection, and a resumption of restraint following retaliation. after a simulated a ...	1985	17793772
bioaccumulation of heavy metals in pre-fledgling tree swallows, tachycineta bicolor.		1989	2790248
impacts of acid rainon aquatic birds.	studies of toxicological and ecological effects of acidification on aquatic birds in europe and north america are reviewed. heavy metals are deposited by acid emissions, which also increase solubility and mobility of heavy metals in soil and water. aluminium is leached from soil and mobilized from lake sediments under acid conditions; it removes susceptible fish and invertebrate species and contaminates remaining invertebrates. it is not highly toxic to birds, but may interfere with their regula ...	1989	24249190
natural selection on body size and laying date in the tree swallow.	i measured natural selection on body size and laying date in a population of tree swallows (tachycineta bicolor) from 1986 to 1988. there was little evidence of selection on body size associated with overwinter survival. disruptive selection on tarsus length, associated with female reproductive success, was detected in one of three years. both repeatability and mother-daughter regression suggested that laying date was heritable. i found weak evidence of selection on laying date, associated with ...	1991	28564184
bioenergetics-based model for accumulation of polychlorinated biphenyls by nestling tree swallows, tachycineta bicolor.		1995	22200268
accumulation in and effects of lead and cadmium on waterfowl and passerines in northern idaho.	waterfowl and passerines in northern idaho in 1987 had high levels of lead in their blood and tissues that originated primarily from mining and smelting activities. four canada geese (branta canadensis) and one common goldeneye (bucephala clangula) found dead contained 8 to 38 microg/g (wet mass) of lead in their livers. these levels exceed the lower lethal limit of 5 microg/g in experimental birds. two of the canada geese (one each from the contaminated and reference areas) died with ingested l ...	1995	15091521
parent-offspring recognition in tree swallows, tachycineta bicolor	parent-offspring recognition appears to be highly developed in species in which the risk of misdirecting care is high (e.g. colonial species). some of the best evidence for this relationship comes from comparative work on swallows of the family hirundinidae. using methods followed in earlier studies, we determined whether parent-offspring recognition occurs in the tree swallow, tachycineta bicolora non-colonial species closely related to the highly colonial bank swallow, riparia ripariaand the s ...	1997	9398366
health of tree swallows (tachycineta bicolor) nesting in pesticide-sprayed apple orchards in ontario, canada. ii. sex and thyroid hormone concentrations and testes development.	to investigate the effects of pesticides on wild birds, sex (17beta-estradiol; testosterone) and thyroid (triiodothyronine (t3) hormone concentrations, body mass, and testes mass were measured and the development of testes was evaluated in wild tree swallows (tachycineta bicolor) nesting in four sprayed apple orchards and three nonsprayed sites in southern ontario, canada, in 1995-1996. in orchards, birds were exposed to asmany as 11 individual spray events and five sprays of mixtures of chemica ...	1998	9885998
health of tree swallows (tachycineta bicolor) nesting in pesticide-sprayed apple orchards in ontario, canada. i. immunological parameters.	the degree of pesticide exposure and its effects on the immune system and its development were determined in 16-d-old tree swallow (tachycineta bicolor) chicks from 4 sprayed apple orchards and three nonsprayed sites in southern ontario, canada, during 1994-1995. persistent contaminant residues were measured in tree swallow eggs and in each chick hepatic ethoxyresorufin o-deethylase (erod) activity; body, immune organ, and liver masses; lymphocyte blastogenesis response; respiratory burst and ph ...	1998	9885997
certainty of paternity and paternal investment in eastern bluebirds and tree swallows.	extra-pair paternity is common in many socially monogamous passerine birds with biparental care. thus, males often invest in offspring to which they are not related. models of optimal parental investment predict that, under certain assumptions, males should lower their investment in response to reduced certainty of paternity. we attempted to reduce certainty of paternity experimentally in two species, the eastern bluebird, sialia sialis, and the tree swallow, tachycineta bicolor, by temporarily ...	1998	9632472
microbes in tree swallow semen.	a frequently hypothesized but poorly studied cost of multiple mating in birds is that exposure to pathogenic sexually transmitted microbes (stm's) can lower reproductive success. conversely, female birds may benefit from high frequencies of copulation and multiple copulation partners if they receive cloacal inoculations of beneficial stm's that can either protect them against future encounters with pathogens and/or serve as therapy against present infection. we examined the semen of 30 male tree ...	2000	10941730
reproductive success and chlorinated hydrocarbon contamination in tree swallows (tachycineta bicolor) nesting along rivers receiving pulp and paper mill effluent discharges.	the insectivorous tree swallow was chosen as an indicator species to investigate the uptake of pulp mill-related chlorinated hydrocarbons from emergent aquatic insects. nest box populations were monitored for reproductive success at locations upstream and downstream of pulp mills on two river systems in british columbia, canada. also, 16-day-old nestlings were collected and analysed for polychlorinated biphenyls (pcbs), polychlorinated dibenzo-p-dioxins (pcdds) and dibenzofurans (pcdfs), pestici ...	2000	15092845
effect of brood size manipulation on offspring physiology: an experiment with passerine birds.	the environment experienced during ontogeny has a significant impact on the physiological condition of offspring. this, in turn, forecasts survival probabilities and future reproductive potential. despite the prominent role that the concept of condition plays in evolutionary studies, the physiological and biochemical characters that define it remain relatively unexplored. in this study, we quantified the impact of brood size manipulations on the physiology and biochemistry of nestling tree swall ...	2000	11044389
offspring sex ratios in tree swallows: females in better condition produce more sons.	organisms are expected to adjust the sex ratio of their offspring in relation to the relative fitness benefits of sons and daughters. we used a molecular sexing technique that amplifies an intron of the chd1 gene in birds to examine the sex ratio at egg-laying in socially monogamous tree swallows (tachycineta bicolor). we examined all individuals in 40 broods (210 young), including all unhatched eggs and nestlings. thus, the sex ratio we measured was the same as the sex ratio at laying. overall, ...	2000	10964231
polychlorinated biphenyl contamination and minisatellite dna mutation rates of tree swallows.	the evidence that exposure to polychlorinated biphenyls (pcbs) leads to mutations is equivocal and controversial. using multilocus dna fingerprinting, we compared the mutation rate of tree swallows (tachycineta bicolor) nesting at sites with high and low levels of contamination with pcbs. the upper hudson river, usa, is highly contaminated with pcbs as a result of releases from two capacitor manufacturing plants in hudson falls and fort edward, new york, usa. tree swallows nesting nearby have so ...	2001	11596759
the effects of experimental reservoir creation on the bioaccumulation of methylmercury and reproductive success of tree swallows (tachycineta bicolor).	reservoir creation results in decomposition of flooded organic matter and increased rates of mercury methylation. methylmercury (mehg), the most toxic form of mercury, bioaccumulates through aquatic food webs. our objective was to quantify the transfer of mehg from aquatic food webs into terrestrial organisms. we examined rates of mehg bioaccumulation in an insectivorous songbird, the tree swallow, breeding near an experimentally created reservoir. we also determined the impact of flooding and m ...	2001	11357867
polycyclic aromatic hydrocarbons, aliphatic hydrocarbons, trace elements, and monooxygenase activity in birds nesting on the north platte river, casper, wyoming, usa.	tree swallow (tachycineta bicolor) and house wren (troglodytes aedon) eggs and chicks were collected near a refinery site on the north platte river, casper. wyoming, usa and at a reference site 10 km upstream. total polycyclic aromatic hydrocarbon (pah) concentrations in swallow and wren chicks were higher at the refinery site than at the reference site. polycyclic aromatic hydrocarbon concentrations in sediment and chick dietary samples were consistent with these findings. the general lack of m ...	2001	11349865
physiological and biochemical correlates of brood size and energy expenditure in tree swallows.	intra-population variation in many fitness-related traits (e.g. clutch size) is often attributed to variation in individual parental quality. one possible component of quality is the level at which each individual can expend energy while provisioning dependent young. we used breeding tree swallows (tachycineta bicolor) to test whether adults with large, natural-sized broods and/or nestlings in good nutritional condition had relatively high daily energy expenditures (dees). adults with high dees ...	2001	11273810
acoustic signalling of hunger and thermal state by nestling tree swallows.	the begging displays used by altricial nestling birds to solicit care from parents include vigorous movements and loud calling. these begging signals have attracted considerable interest, mainly because their intensity seems excessive for the function of transmitting information about nestling need to parents. however, how information on need is encoded in the various components of the signal, especially its acoustic components, is poorly understood. we examined how begging calls of large and sm ...	2001	11170699
high levels of extra-pair paternity in an isolated, low-density, island population of tree swallows (tachycineta bicolor).	molecular genetic studies have suggested that apparently nonbreeding males ('floaters') may account for a significant proportion of extra-pair paternity (epp) in avian populations. attempts to determine the influence of breeding density on epp are therefore confounded by the presence of a subpopulation of floaters whose numbers are difficult to estimate. to study epp in a tree swallow (tachycineta bicolor) population with few floaters, we chose a nestbox grid on an island with an excess of avail ...	2001	11380885
dioxins and congener-specific polychlorinated biphenyls in three avian species from the wisconsin river, wisconsin.	sediments from the wisconsin river. wi. usa are contaminated with 2,3,7,8-tetrachloro-p-dioxin (tcdd) and polychlorinated biphenyls (pcbs). wet weight concentrations of tcdd and pcbs in eggs were at background levels and highest in the piscivorous = 7 pg/g tcdd a hooded merganser (lophodytes cucullatus; geometric m ean nd 0.92 microg/g pcbs) a nd lowest in the omnivorous wood duck (aix sponsa) (< 1 pg/g and 0.07 microg/g); concentrations in eggs of the insectivorous tree swallow (tachycineta bic ...	2002	12166666
health of tree swallow (tachycineta bicolor) nestlings exposed to chlorinated hydrocarbons in the st lawrence river basin. part i. renal and hepatic vitamin a concentrations.	sixteen-day-old tree swallows (tachycineta bicolor), near fledging, were collected in 1999 and 2000 from nine sites representing a gradient of dioxin concentrations, within the vicinity of the st. lawrence river in canada and the united states, to determine if organochlorine contaminants correlated with vitamin a levels measured as retinol and retinyl palmitate. mean concentrations of hepatic retinol ranged from 3 mg /kg to 13 mg /kg, and from 0.35 mg /kg to 1.5 mg /kg for renal retinol. mean co ...	2003	12775516
reproductive effort reduces long-term immune function in breeding tree swallows (tachycineta bicolor).	we examined whether strategies of reproductive allocation may reduce long-term immunocompetence through the effects of manipulated effort on secondary or acquired immunity. we tested whether increased reproductive effort leads to reduced immune function and survival by manipulating brood size in tree swallows (tachycineta bicolor) and exposing breeding females to a primary and secondary exposure of sheep red blood cells to elicit a humoral immune response. females raising enlarged broods produce ...	2003	12964994
health of tree swallow (tachycineta bicolor) nestlings exposed to chlorinated hydrocarbons in the st. lawrence river basin. part ii. basal and stress plasma corticosterone concentrations.	sixteen-day-old tree swallows (tachycineta bicolor) were collected in 1999 and 2000 from nine sites within the vicinity of the st. lawrence river in canada and the united states to determine if organochlorine contaminant concentrations correlated with corticosterone levels. basal plasma corticosterone levels were determined in chicks reared in nest boxes, and stress plasma corticosterone levels were determined in chicks after exposure to a 10-min standardized stress test. mean basal plasma corti ...	2003	14555399
digenetic trematodes, acanthatrium sp. and lecithodendrium sp., as vectors of neorickettsia risticii, the agent of potomac horse fever.	neorickettsia (formerly ehrlichia) risticii, the agent of potomac horse fever (phf), has been recently detected in trematode stages found in the secretions of freshwater snails and in aquatic insects. insectivores, such as bats and birds, may serve as the definitive host of the trematode vector. to determine the definitive helminth vector, five bats (myotis yumanensis) and three swallows (hirundo rustica, tachycineta bicolor) were collected from a phf endemic location in northern california. bat ...	2003	14627451
exposure and effects of chemical contaminants on tree swallows nesting along the housatonic river, berkshire county, massachusetts, usa, 1998-2000.	hatching success of tree swallows (tachycineta bicolor) was assessed for three years in relation to chemical contamination along the housatonic river, berkshire county (ma, usa), in 1998, 1999, and 2000. nest boxes were erected at five sites along the housatonic river and its tributaries and at one reference location. concentrations of total polychlorinated biphenyls (pcbs) were some of the highest ever reported in bird eggs. mean concentrations at sites along the housatonic river ranged between ...	2003	12836988
accumulation of pcb congeners in nestling tree swallows (tachycineta bicolor) on the hudson river, new york.	tree swallows (tachycineta bicolor) were used as a sentinel species to monitor the contamination and bioavailability of polychlorinated biphenyls (pcbs) in the hudson river watershed. several tree swallow nest box colonies around and downstream from hudson falls, ny, were studied. tree swallow eggs, adults, and 5-, 10-, and 15-day-old nestlings were collected and analyzed for 103 pcb congeners. emergent insects collected by net (primarily odonata) or as a food bolus (primarily diptera) taken fro ...	2004	15597877
stress and immune responses of nestling tree swallows (tachycineta bicolor) and eastern bluebirds (sialia sialis) exposed to nonpersistent pesticides and p,p'-dichlorodiphenyldichloroethylene in apple orchards of southern ontario, canada.	to determine the relative effects of pesticides in current use and persistent residues of p,p'-dichlorodiphenyldichloroethylene (p,p'-dde), we examined endocrine and immune responses in tree swallow (tachycineta bicolor) and eastern bluebird (sialia sialis) chicks from pesticide-sprayed apple orchards and reference sites in southern ontario, canada, during 2000 to 2001. nests were exposed to as many as seven individual pesticide applications and up to five mixtures of pesticides during the egg-i ...	2004	15648768
thyroid function in nestling tree swallows and eastern bluebirds exposed to non-persistent pesticides and p, p'-dde in apple orchards of southern ontario, canada.	this study examined the associated effects of pesticides and persistent residues of p,p'-dde on thyroid function in 16-day-old tree swallows (tachycineta bicolor) and 12-day-old eastern bluebirds (sialia sialis). apple orchards sprayed with pesticides in current use and reference sites were chosen for study in southern ontario, canada, during 2000-2001. we assessed thyroid hormone concentrations (plasma and muscle thyroxine [t4], and triiodothyronine [t3]) and the response to a challenge with th ...	2005	15943111
spatial, temporal, and dietary determinants of organic contaminants in nestling tree swallows in point pelee national park, ontario, canada.	point pelee national park of canada in southwestern ontario, an important migratory route and vital breeding area for many birds, has localized areas of organochlorine (oc) pesticide contamination from agricultural production during the 1950s and 1960s. during 2001 and 2002, we investigated movement of persistent contaminants through the food web with the insectivorous tree swallow (tachycineta bicolor) as a sentinel. the a priori site classifications, contaminated or reference, were based on so ...	2005	16445099
reproductive success and contaminants in tree swallows (tachycineta bicolor) breeding at a wastewater treatment plant.	the uptake and effects of contaminants were measured in the insectivorous tree swallow (tachycineta bicolor) at a wastewater treatment site. the study examined reproductive, immunological, and growth endpoints in tree swallows exposed to chlorinated hydrocarbon contaminants and to 4-nonylphenol in wastewater lagoons at the iona wastewater treatment plant, vancouver (bc, canada). clutch size was significantly lower in tree swallows breeding at iona island in 2000 and 2001 compared to the referenc ...	2005	16445092
organochlorine contamination and physiological responses in nestling tree swallows in point pelee national park, canada.	point pelee national park in southwestern ontario, canada--a major migratory route and vital breeding area for many birds--has localized areas of organochlorine (oc) contamination from the 1950s and 1960s. during 2002, we investigated the effect of tissue oc contaminant levels on the physiology and growth of nestling tree swallows (tachycineta bicolor). polychlorinated biphenyl (pcb) contamination in the nestlings positively correlated with hepatic ethoxy-, benzyloxy-, and pentoxyresorufin-o-dea ...	2005	16205989
maternal influences on brood sex ratios: an experimental study in tree swallows.	when the reproductive value of sons and daughters differ, parents are expected to adjust the sex ratio of their offspring to produce more of the sex that provides greater fitness returns. the body condition of females or environmental factors, such as food abundance and mate quality, may influence these expected fitness returns. in a previous study of tree swallows (tachycineta bicolor), we found that females produced more sons in their broods when they were in better body condition (mass correc ...	2005	16096088
the importance of microclimate variation in determining size, growth and survival of avian offspring: experimental evidence from a cavity nesting passerine.	organisms are expected to balance energy allocation in such a way that fitness is maximized. while much research has focussed on allocation strategies of reproducing parents, in particular birds, relatively little attention has been paid to how nestlings allocate energy while in the nest. nestling birds are faced with a trade-off between devoting energy to growth or to thermoregulation, and in altricial species it is likely that the thermal environment of the nest site influences the nature of t ...	2005	15891832
ambient noise and the design of begging signals.	the apparent extravagance of begging displays is usually attributed to selection for features, such as loud calls, that make the signal costly and hence reliable. an alternative explanation, however, is that these design features are needed for effective signal transmission and reception. here, we test the latter hypothesis by examining how the begging calls of tree swallow (tachycineta bicolor) nestlings and the response to these calls by parents are affected by ambient noise. in a field study, ...	2005	15817440
exposure and effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin in tree swallows (tachycineta bicolor) nesting along the woonasquatucket river, rhode island, usa.	concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (tcdd) in tree swallows (tachycineta bicolor) nesting along the woonasquatucket river northwest of providence (ri, usa) in 2000 and 2001 were some of the highest ever reported in avian tissues. mean concentrations in eggs ranged from 300 to >1,000 pg/g wet weight at the two most contaminated ponds, allendale and lyman. mean egg concentrations at greystone, the upstream reference pond, were 12 and 29 pg/g. positive accumulation rates and conce ...	2005	15683172
longer telomeres associated with higher survival in birds.	differences in individual quality and survival within species are a major focus in evolutionary ecology, but we know very little about the underlying physiological mechanisms that determine these differences. telomere shortening associated with cellular senescence and ageing may be one such mechanism. to date, however, there is little evidence linking telomere length and survival. here, we show that tree swallows (tachycineta bicolor) with relatively short telomeres at the age of 1 year have low ...	2005	17148169
trace element concentrations and bioindicator responses in tree swallows from northwestern minnesota.	extremely high concentrations of cadmium (3.5 microg/g dry wgt.) and elevated concentrations of chromium (>10 microg/g dry wgt.) and mercury (1.6 microg/g dry wgt.) were reported in waterbird tissues at agassiz national wildlife refuge in northwestern minnesota in 1994. tree swallows (tachycineta bicolor) were studied during 1998-2001 at three drainages into the refuge, two pools on the refuge, and at a nearby reference location to document whether high levels of contaminants were still present, ...	2006	16897545
bioaccumulation and trophic transfer of polychlorinated biphenyls by aquatic and terrestrial insects to tree swallows (tachycineta bicolor).	insectivorous passerines often bioaccumulate polychlorinated biphenyls (pcbs) via trophic transfer processes. tree swallows (tachycineta bicolor) frequently are used for estimating pcb bioaccumulation, yet the focus on specific trophic links between contaminated sediment and bird has been limited. bioaccumulation of pcbs from sediment to tree swallows was examined with focus on trophic pathways by simultaneously examining pcbs in emergent aquatic and terrestrial insects and gut contents of nestl ...	2006	16629140
tree swallow (tachycineta bicolor) exposure to polychlorinated biphenyls at the kalamazoo river superfund site, michigan, usa.	in 1990, a portion of the kalamazoo river in michigan, usa, was designated a superfund site because of the presence of polychlorinated biphenyls (pcbs) in the sediment and floodplain soils. during a four-year period from 2000 to 2003, several avian species were monitored for reproductive effects and concentrations of pcbs in tissues attributed to food chain transfer from contaminated sediments. the tree swallow (tachycineta bicolor) was chosen as a model receptor for contamination of passerine s ...	2006	16519303
repeatability of extra-pair mating in tree swallows.	models of sexual selection assume that female mating preferences are heritable and, thus, repeatable for individual females across multiple mating episodes. previous studies of the repeatability of female preference have examined individuals in captivity and focused presumably on social mate choice. however, extra-pair mating is widespread and can also influence sexual selection. we examined the repeatability of extra-pair mating in a wild population of tree swallows (tachycineta bicolor) by exp ...	2006	16499706
productivity of tree swallows (tachycineta bicolor) exposed to pcbs at the kalamazoo river superfund site.	a 123-km stretch of the kalamazoo river in michigan, was designated a superfund site in 1990 due to historical releases of effluent containing polychlorinated biphenyl (pcb)-contaminated paper waste. risk to bird species in the river ecosystem was evaluated using the tree swallow (tachycineta bicolor) as a monitor for possible effects due to pcb exposure at two nesting locations, one in the superfund site and one in an upstream reference location that is less contaminated with pcbs. in 2 of the ...	2006	16455617
time and recruitment costs as currencies in manipulation studies on the costs of reproduction.	life history theory predicts that parents will have lower darwinian fitness if they tend clutches that are above or below the size they naturally produce. we experimentally tested for relationships between fitness and clutch size in tree swallow (tachycineta bicolor) offspring and parents. over 130 trios of nests initiated on the same day were randomly divided among reduce (-3 eggs), control (3 eggs picked up and replaced), or add (+3 eggs) manipulations. pre-manipulation modal clutch size was s ...	2006	17168037
evaluating cytochrome p450 in lesser scaup (aythya affinis) and tree swallow (tachycineta bicolor) by monooxygenase activity and immunohistochemistry: possible nonlethal assessment by skin immunohistochemistry.	six-month-old lesser scaup (aythya affinis) and nestling tree swallows (tachycineta bicolor) were injected intraperitoneally with beta-naphthoflavone (bnf) in corn oil or in vehicle alone. liver samples were taken and stored at -80 degrees c until microsome preparation and monooxygenase assay. skin samples were placed in buffered formalin for subsequent immunohistochemical (ihc) analysis for cytochrome p4501a (cyp1a). lesser scaup treated with bnf at 20 or 100 mg/kg body weight showed approximat ...	2006	17022400
effects of oil sands tailings compounds and harsh weather on mortality rates, growth and detoxification efforts in nestling tree swallows (tachycineta bicolor).	oil sands mining companies in alberta, canada, are evaluating the feasibility of using wetlands to detoxify oil sands process material (ospm) as a reclamation strategy. reproductive success, nestling growth, survival and ethoxyresorufin-o-deethylase (erod) activity were measured in tree swallows (tachycineta bicolor) on experimental wetlands. in 2003, harsh weather triggered a widespread nestling die-off. mortality rates on the control site reached 48% while they ranged from 59% to 100% on recla ...	2006	16297515
polychlorinated biphenyl congener patterns in tree swallows (tachycineta bicolor) nesting in the housatonic river watershed, western massachusetts, usa, using a novel statistical approach.	a novel application of a commonly used statistical approach was used to examine differences in polychlorinated biphenyl (pcb) congener patterns among locations and sample matrices in tree swallows (tachycineta bicolor) nesting in the housatonic river watershed in western massachusetts, usa. the most prevalent pcb congeners in tree swallow tissue samples from the housatonic river watershed were ballsmitter zell numbers 153, 138, 180, 187, 149, 101, and 170. these congeners were seven of the eight ...	2006	16377044
external heart deformities in passerine birds exposed to environmental mixtures of polychlorinated biphenyls during development.	necropsy-observable cardiac deformities were evaluated from 283 nestling passerines collected from one reference site and five polychlorinated biphenyl (pcb)-contaminated sites around bloomington and bedford, indiana, usa. hearts were weighed and assessed on relative scales in three dimensions (height, length, and width) and for externally visible deformities. heart weights normalized to body weight (heart somatic index) were decreased significantly at the more contaminated sites in both house w ...	2006	16519318
interindividual variability in body composition and resting oxygen consumption rate in breeding tree swallows, tachycineta bicolor.	basal metabolic rate is one of the most widely measured physiological traits. previous studies on lab mice and field-caught lizards suggest that individuals with relatively high basal metabolic rates or standard metabolic rates have relatively large masses of metabolically active tissues (e.g., heart, kidney, liver). as these are energetically expensive organs, there may be variability between breeding seasons dependent on, for example, availability of prey and capacity for energy intake. we pre ...	2006	9634171
adult tree swallow (tachycineta bicolor) survival on the polychlorinated biphenyl-contaminated housatonic river, massachusetts, usa.	tree swallows (tachycineta bicolor) were captured and banded at six sites that differed in polychlorinated biphenyl (pcb) contamination levels in the housatonic river watershed, western massachusetts, usa, from 2000 through 2004 to test the prediction that apparent survival rates of females in more contaminated areas were lower than those from less contaminated areas. we also tested whether plumage coloration affected over-winter survival and whether concentrations of pcbs in eggs differed betwe ...	2007	17521155
pcb congener profiles in nestling tree swallows and their insect prey.	tree swallows (tachycineta bicolor) are widely used as indicators of local polychlorinated biphenyl (pcb) contamination in north america. although determining total pcb residues in tissues is useful in environmental monitoring, analysis of pcb congener profiles may reveal sources of contamination and thus prove to be a more refined tool to track contaminants through the food web. to show how differences in pcb congener patterns in birds can be linked to the pcb patterns in their prey, we evaluat ...	2007	17165104
mercury exposure and effects on cavity-nesting birds from the carson river, nevada.	mercury (hg) concentrations were 15-40 times higher in the eggs and livers of tree swallows (tachycineta bicolor) and house wrens (troglodytes aedon) that nested along the carson river at and below dayton, nevada than in the same species above the mining-impacted areas. hg contamination was mainly the result of processing mills in the 1800s that used hg to separate gold and silver from ore. the exposure pattern of tree swallows and house wrens along the carson river was consistent with their tro ...	2007	17083002
mercury and growth of tree swallows at acadia national park, and at orono, maine, usa.	in 1997 and 1998 we weighed nestling tree swallows (tachycineta bicolor) and measured selected body components at two colonies: acadia national park on mt. desert island, and at orono, me. we used differences in mean growth variables among individual nestlings to evaluate differences between colonies, years, and amount of total mercury (thg) in carcasses and methyl mercury (mehg) in feathers. we marked nestlings on the day hatched and measured body components every day in 1997 and every other da ...	2007	17057986
mercury in tree swallow food, eggs, bodies, and feathers at acadia national park, maine, and an epa superfund site, ayer, massachusetts.	we monitored nest boxes during 1997-1999 at acadia national park, mt. desert island, me and at an old-field site in orono, me to determine mercury (hg) uptake in tree swallow (tachycineta bicolor) eggs, tissues, and food boluses. also, in 1998-1999 we monitored nest boxes at grove pond and plow shop pond at a u.s. environmental protection agency superfund site in ayer, ma. we recorded breeding success at all locations. on average among locations, total mercury (thg) biomagnified 2 to 4-fold from ...	2007	16957848
effects of exposure to naphthenic acids in tree swallows (tachycineta bicolor) on the athabasca oil sands, alberta, canada.	naphthenic acids (nas) are a group of carboxylic acids that are of particular concern to the steadily growing oil sands mining industry of alberta, canada, because they become highly concentrated in the water used for oil sands extraction and are toxic to aquatic biota and mammals. upon mine closure, vast amounts of process-affected water will need to be reclaimed and proven safe for wildlife colonizing reclaimed areas. the effects of exposure to nas have not been investigated in avian species. ...	2007	17573632
increased thyroid hormone levels in tree swallows (tachycineta bicolor) on reclaimed wetlands of the athabasca oil sands.	the oil sands of alberta, canada are one of the world's largest reserves of crude oil. oil sands mining companies are now investigating the ecological impacts of reclamation strategies in which wetlands are used for the bioremediation of waste materials. to examine the endocrine disrupting potential of chemicals in oil sands process materials (ospm), thyroid hormone concentrations were measured in plasma and thyroid glands of nestling tree swallows (tachycineta bicolor) from wetlands partly fill ...	2007	17549538
tree swallows (tachycineta bicolor) nesting on wetlands impacted by oil sands mining are highly parasitized by the bird blow fly protocalliphora spp.	oil sands mining is steadily expanding in alberta, canada. major companies are planning reclamation strategies for mine tailings, in which wetlands will be used for the bioremediation of water and sediments contaminated with polycyclic aromatic hydrocarbons and naphthenic acids during the extraction process. a series of experimental wetlands were built on companies' leases to assess the feasibility of this approach, and tree swallows (tachycineta bicolor) were designated as upper trophic biologi ...	2007	17495301
water level management and contaminant exposure to tree swallows nesting on the upper mississippi river.	the u.s. army corps of engineers conducted a water drawdown on navigation pool 8 of the upper mississippi river during the summers of 2001 and 2002 to increase aquatic vegetation production and thereby improve fish and wildlife habitat. flooding of previously dried wetlands, however, may increase the rate of mercury methylation and make mercury more available to terrestrial vertebrates that feed in aquatic environments. our objective was to determine if mercury, other elements, and organochlorin ...	2007	17286172
immunosenescence in some but not all immune components in a free-living vertebrate, the tree swallow.	a wide diversity of free-living organisms show increases in mortality rates and/or decreases in reproductive success with advancing age. however, the physiological mechanisms underlying these demographic patterns of senescence are poorly understood. immunosenescence, the age-related deterioration of immune function, is well documented in humans and laboratory models, and often leads to increased morbidity and mortality due to disease. however, we know very little about immunosenescence in free-l ...	2007	17251097
experimental heating reveals nest temperature affects nestling condition in tree swallows (tachycineta bicolor).	investment in one life-history stage can have delayed effects on subsequent life-history stages within a single reproductive bout. we experimentally heated tree swallow (tachycineta bicolor) nests during incubation to test for effects on parental and nestling conditions. females incubating in heated boxes maintained higher body condition and fed nestlings at higher rates. we cross-fostered nestlings and found that young nestlings (4-7 days old) incubated in heated nests had higher body condition ...	2008	18628112
patterns of variation in leucocyte counts of female tree swallows, tachycineta bicolor: repeatability over time and relationships with condition and costs of reproduction.	the heterophil to lymphocyte (hl) ratio in the peripheral blood is increasingly being recognized as a reliable indicator of stress in birds. in this study we examined whether hl ratio, as well as the proportion of heterophils and lymphocytes, varied systematically with sampling time, date, age, climate conditions or with measures of maternal investment in female tree swallows (tachycineta bicolor) over three breeding seasons. we found that hl ratios showed significant annual variation, which app ...	2008	18485771
corticosterone stress response in tree swallows nesting near polychlorinated biphenyl- and dioxin-contaminated rivers.	we assayed baseline and stress-induced corticosterone concentrations from adult female and nestling tree swallows, tachycineta bicolor, from new england, u.s.a., sites with different levels of contamination with polychlorinated biphenyls (pcbs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (tcdd). corticosterone was compared over 2 years from a highly contaminated pcb site along the housatonic river (berkshire county, ma, usa), a midrange contaminated site upstream, and a reference site. adult females ...	2008	18476749
laterality and flight: concurrent tests of side-bias and optimality in flying tree swallows.	behavioural side-bias occurs in many vertebrates, including birds as a result of hemispheric specialization and can be advantageous by improving response times to sudden stimuli and efficiency in multi-tasking. however, behavioural side-bias can lead to morphological asymmetries resulting in reduced performance for specific activities. for flying animals, wing asymmetry is particularly costly and it is unclear if behavioural side-biases will be expressed in flight; the benefits of quick response ...	2008	18335028
mercury and other element exposure to tree swallows (tachycineta bicolor) nesting on lostwood national wildlife refuge, north dakota.	elevated mercury concentrations in water were reported in the prairie wetlands at lostwood national wildlife refuge, nd. in order to determine whether wildlife associated with these wetlands was exposed to and then accumulated higher mercury concentrations than wildlife living near more permanent wetlands (e.g. lakes), tree swallow (tachycineta bicolor) eggs and nestlings were collected from nests near seasonal wetlands, semi-permanent wetlands, and lakes. mercury concentrations in eggs collecte ...	2008	18207620
effects of mercury exposure on the reproductive success of tree swallows (tachycineta bicolor).	an experimental tree swallow population was established in the headwaters of the shenandoah river, virginia, usa to assess the accumulation and effects of mercury contamination on birds that eat emergent aquatic insects. one tributary, the south river, was contaminated with mercury before 1950. reproductive success of swallows nesting within 50 m of this river was compared to that of three uncontaminated reference tributaries in 2005 and 2006. female swallows on the contaminated stretch of river ...	2008	17701345
acoustic interactions in broods of nestling birds (tachycineta bicolor).	studies of acoustic interactions in animal groups, such as chorusing insects, anurans, and birds, have been invaluable in showing how cooperation and competition shape signal structure and use. the begging calls of nestling birds are ideal for such studies, because they function both as a cooperative signals of the brood's needs and as competitive signals for parental allocation within the brood. nonetheless, studies of acoustic interactions among nestlings are rare. here we review our work on a ...	2008	18729658
evaluation of polychlorinated biphenyl remediation at a superfund site using tree swallows (tachycineta bicolor) as indicators.	we studied tree swallows (tachycineta bicolor) at the sangamo national priorities list (npl) site and a reference area (little grassy) within crab orchard national wildlife refuge, illinois, usa, to evaluate the bioavailability of polychlorinated biphenyls (pcbs) at the npl site following remediation. tree swallow eggs and 12- to 17-d-old chicks were collected from april to june 2004 and 2005. total egg pcb concentrations in eggs did not differ between years at sangamo; mean concentrations at sa ...	2008	18699698
digit ratio in birds.	the homeobox (hox) genes direct the development of tetrapod digits. the expression of hox genes may be influenced by endogenous sex steroids during development. manning (digit ratio. new brunswick, nj: rutgers university press, 2002) predicted that the ratio between the lengths of digits 2 (2d) and 4 (4d) should be sexually dimorphic because prenatal exposure to estrogens and androgens positively influence the lengths of 2d and 4d, respectively. we measured digits and other morphological traits ...	2008	18833568
metal concentrations in three species of passerine birds breeding in the hackensack meadowlands of new jersey.	the new jersey meadowlands is an important natural area, a diverse mosaic of wetland habitats positioned within the heavily urbanized ny city metropolitan area and the ny/nj harbor. persistent contaminants may pose threats to wildlife inhabiting these habitats, affecting reproduction, egg hatchability, nestling survivorship, and neurobehavioral development. metals of concern in the meadowlands include arsenic, cadmium, chromium, lead, and mercury. these metals were analyzed in feathers and blood ...	2008	18191831
breeding success of tree swallows along a gradient of agricultural intensification.	the intensification of agricultural practices has been identified as the main cause of population decline in farmland birds since the 1960s in both europe and north america. although the links between species richness or abundance and various components of agricultural intensification are well established, the mechanisms underlying these trends have rarely been addressed along a gradient of intensification or have been quantified at only one spatial scale. here we quantified the influence of lan ...	2008	18686577
microsatellite evolution: mutations, sequence variation, and homoplasy in the hypervariable avian microsatellite locus hru10.	microsatellites are frequently used genetic markers in a wide range of applications, primarily due to their high length polymorphism levels that can easily be genotyped by fragment length analysis. however, the mode of microsatellite evolution is yet not fully understood, and the role of interrupting motifs for the stability of microsatellites remains to be explored in more detail. here we present a sequence analysis of mutation events and a description of the structure of repeated regions in th ...	2008	18471288
cliff swallows petrochelidon pyrrhonota as bioindicators of environmental mercury, cache creek watershed, california.	to evaluate mercury (hg) and other element exposure in cliff swallows (petrochelidon pyrrhonota), eggs were collected from 16 sites within the mining-impacted cache creek watershed, colusa, lake, and yolo counties, california, usa, in 1997-1998. nestlings were collected from seven sites in 1998. geometric mean total hg (thg) concentrations ranged from 0.013 to 0.208 microg/g wet weight (ww) in cliff swallow eggs and from 0.047 to 0.347 microg/g ww in nestlings. mercury detected in eggs generally ...	2008	18166988
resource selection plasticity and community responses to experimental reduction of a critical resource.	resource selection plasticity and behavioral dominance may influence the ability of a species to respond to changes in resource availability, particularly if dominant species have highly specialized resource requirements. we examined the response of several dominant and subordinate cavity-nesting species to a reduction in the availability of an essential resource (nesting cavities) using the novel experimental approach of blocking the entrances to high-quality cavities. we monitored nest abundan ...	2008	18481522
compromised immune competence in free-living tree swallows exposed to mercury.	mercury is a pervasive environmental contaminant and a well-documented immunosuppressor. however, little is known about the effects of mercury contamination on health of free-living vertebrate populations. the south river in virginia, usa was heavily contaminated with industrial mercury from 1929 to 1950, and recent studies have documented high levels of circulating mercury in riparian songbirds breeding below the site of contamination. here we used two standardized immune assays, mitogen-induce ...	2009	19322655
species differences in the sensitivity of avian embryos to methylmercury.	we injected doses of methylmercury into the air cells of eggs of 26 species of birds and examined the dose-response curves of embryo survival. for 23 species we had adequate data to calculate the median lethal concentration (lc(50)). based on the dose-response curves and lc(50)s, we ranked species according to their sensitivity to injected methylmercury. although the previously published embryotoxic threshold of mercury in game farm mallards (anas platyrhynchos) has been used as a default value ...	2009	18421496
pcbs and dde in tree swallow (tachycineta bicolor) eggs and nestlings from an estuarine pcb superfund site, new bedford harbor, ma, u.s.a.	while breeding tree swallows (tachycineta bicolor) have been used as biomonitors for freshwater sites, we report the first use of this species to assess contaminant bioaccumulation from estuarine breeding grounds into these aerial insectivores. eggs and nestlings were collected from nest boxes in a polychlorinated biphenyl (pcb) contaminated estuary, the new bedford harbor superfund site (nbh, massachusetts, usa), and a reference salt marsh, fox hill (fh, jamestown, rhode island, usa). sediments ...	2009	19924974
temperature and life history: experimental heating leads female tree swallows to modulate egg temperature and incubation behaviour.	1. life-history decisions are strongly affected by environmental conditions. in birds, incubation is energetically expensive and affected significantly by ambient temperature. we reduced energetic constraints for female tree swallows (tachycineta bicolor) by experimentally heating nests during incubation by an average of 6.9 degrees c to test for changes in incubation behaviour. 2. females in heated boxes (hereafter 'heated females') increased time spent incubating and maintained higher on-bout ...	2009	18637971
non-random distribution of individual genetic diversity along an environmental gradient.	improving our knowledge of the links between ecology and evolution is especially critical in the actual context of global rapid environmental changes. a critical step in that direction is to quantify how variation in ecological factors linked to habitat modifications might shape observed levels of genetic variability in wild populations. still, little is known on the factors affecting levels and distribution of genetic diversity at the individual level, despite its vital underlying role in evolu ...	2009	19414469
the corticosterone stress response and mercury contamination in free-living tree swallows, tachycineta bicolor.	we determined mercury concentrations in tree swallows, tachycineta bicolor, from massachusetts and maine with different levels of contamination. baseline and stress-induced plasma corticosterone concentrations from adults and nestlings (massachusetts only) were compared with mercury concentrations. in massachusetts, adult baseline corticosterone was negatively correlated with blood mercury, but showed a nearly-significant positive correlation with feather mercury. there was a negative relationsh ...	2009	19360470
geographic variation of strontium and hydrogen isotopes in avian tissue: implications for tracking migration and dispersal.	isotopes can provide unique solutions to fundamental problems related to the ecology and evolution of migration and dispersal because prior movements of individuals can theoretically be tracked from tissues collected from a single capture. however, there is still remarkably little information available about how and why isotopes vary in wild animal tissues, especially over large spatial scales.	2009	19266102
the relationship between fitness and baseline glucocorticoids in a passerine bird.	glucocorticoid (cort) hormones are increasingly applied in studies of free-ranging animals, with elevated baseline cort levels generally assumed to indicate individuals or populations in worse condition and with lower fitness (the cort-fitness hypothesis). the relationship between cort and fitness is rarely validated and studies investigating the cort-fitness relationship often find results inconsistent with the cort-fitness hypothesis. the inconsistency of these studies may result in part from ...	2009	19135999
ontogeny of innate and adaptive immune defense components in free-living tree swallows, tachycineta bicolor.	little is known about the development of immune function in wild animals. we investigated the ontogeny of immune defense in a free-living bird, the tree swallow. we assessed total and differential leukocyte counts, natural antibodies, complement activity, in vivo skin swelling response, and in vitro lymphocyte proliferation and compared the levels of development between nestlings and young adults. we also assessed whether body condition explained variation in these immune components. we found so ...	2009	18848578
experimental evidence that keeping eggs dry is a mechanism for the antimicrobial effects of avian incubation.	avian incubation dramatically reduces the abundance and diversity of microbial assemblages on eggshells, and this effect has been hypothesized as an adaptive explanation for partial incubation, the bouts of incubation that some birds perform during the egg-laying period. however, the mechanisms for these antimicrobial effects are largely unknown. in this study, we hypothesized that microbial inhibition is partly achieved through removal of liquid water, which generally enhances microbial growth, ...	2010	21057768
relationship between laying sequence and mercury concentration in tree swallow eggs.	when female birds lay eggs, some of their body burden of mercury is eliminated into each egg, potentially leading to declining mercury across the clutch. however, there was no decline in mercury with laying sequence in clutches of tree swallow (tachycineta bicolor) eggs at a mercury-contaminated site, presumably due to daily replenishment of mercury in females during laying. sampling just one egg from the nest provided an accurate measure of clutch mercury contamination.	2010	20821552
effects of egg order on organic and inorganic element concentrations and egg characteristics in tree swallows, tachycineta bicolor.	the laying order of tree swallow eggs was identified from the housatonic river, berkshire county, massachusetts, usa, and eggs were chemically analyzed individually to document possible effects of laying order on organic contaminant and inorganic element concentrations. effects of laying order on other parameters such as egg weight, size, and lipid and moisture content also were assessed. some effects of egg order on total polychlorinated biphenyls (pcbs) were detected, but the effect was not un ...	2010	20821521
fitness benefits of polyandry for experienced females.	females often mate with several different males, which may promote sperm competition and increase offspring viability. however, the potential benefits of polyandry remain controversial, particularly in birds where recent reviews have suggested that females gain few genetic benefits from extra-pair mating. in tree swallows (tachycineta bicolor), we found that females with prior breeding experience had more sires per brood when paired to genetically similar social mates, and, among experienced fem ...	2010	20444084
experimental cooling during incubation leads to reduced innate immunity and body condition in nestling tree swallows.	nest microclimate can have strong effects that can carry over to later life-history stages. we experimentally cooled the nests of tree swallows (tachycineta bicolor). females incubating in cooled nests reduced incubation time and allowed egg temperatures to drop, leading to extended incubation periods. we partially cross-fostered nestlings to test carry-over effects of cooling during incubation on nestling innate constitutive immunity, assessed through bacteria killing ability (bka) of blood. ne ...	2010	20147326
spatiotemporal exploratory models for broad-scale survey data.	the distributions of animal populations change and evolve through time. migratory species exploit different habitats at different times of the year. biotic and abiotic features that determine where a species lives vary due to natural and anthropogenic factors. this spatiotemporal variation needs to be accounted for in any modeling of species' distributions. in this paper we introduce a semiparametric model that provides a flexible framework for analyzing dynamic patterns of species occurrence an ...	2010	21265447
variation in immune function, body condition, and feather corticosterone in nestling tree swallows (tachycineta bicolor) on reclaimed wetlands in the athabasca oil sands, alberta, canada.	in the athabasca oil sands region of northern alberta, mining companies are evaluating reclamation using constructed wetlands for integration of tailings. from may to july 2008, reproductive performance of 40 breeding pairs of tree swallows (tachycineta bicolor), plus growth and survival of nestlings, was measured on three reclaimed wetlands on two oil sands leases. a subset of nestlings was examined for i) feather corticosterone levels, ii) delayed-type hypersensitivity response, and iii) innat ...	2010	19850385
polychlorinated biphenyls, dioxins, furans, and organochlorine pesticides in spotted sandpiper eggs from the upper hudson river basin, new york.	in 2004, spotted sandpipers (actitis macularia) were studied on the hudson river near fort edward south to new baltimore, ny and on two river drainages that flow into the hudson river. concentrations of 28 organochlorine pesticides, 160 polychlorinated biphenyl (pcb) congeners, and 17 dioxin and furan (pcdd-f) congeners were quantified in eggs collected on and off the hudson river. the pattern of organochlorine pesticides and pcdd-f congeners did not differ significantly between eggs collected o ...	2010	19809875
patterns of organic contaminants in eggs of an insectivorous, an omnivorous, and a piscivorous bird nesting on the hudson river, new york, usa.	belted kingfisher (ceryle alcyon), spotted sandpiper (actitus macularia), and tree swallow (tachycineta bicolor) eggs were collected in 2004 from the upper hudson river, new york, usa. this area is one of the most polychlorinated biphenyl (pcb)-contaminated locations in north america. multivariate analyses indicated among species differences in the concentration and composition of pcb congeners, polychlorinated dibenzo-p-dioxin (pcdd), and dibenzofuran (pcdf, pcdd-f when combined with pcdds) con ...	2010	20872693
passerine exposure to primarily pcdfs and pcdds in the river floodplains near midland, michigan, usa.	house wren (troglodytes aedon), tree swallow (tachycineta bicolor), and eastern bluebird (sialia sialis) tissues collected in study areas (sas) downstream of midland, michigan (usa) contained concentrations of polychlorinated dibenzofurans (pcdfs) and polychlorinated dibenzo-p-dioxins (pcdds) greater than in upstream reference areas (ras) in the region. the sum of concentrations of pcdd/dfs (sigmapcdd/dfs) in eggs of house wrens and eastern bluebirds from sas were 4- to 22-fold greater compared ...	2010	19894014
microbial and environmental effects on avian egg viability: do tropical mechanisms act in a temperate environment?	the viability of freshly laid avian eggs declines after several days of exposure to ambient temperatures above physiological zero, and declines occur faster in tropical than temperate ecosystems. microbial infection during preincubation exposure has recently been shown as a second cause of egg viability decline in the tropics, but whether microbial processes influence the viability of wild bird eggs in temperate ecosystems is unknown. we determined the microbial load on eggshells, the incidence ...	2011	21661574
dietary exposure of three passerine species to pcdd/dfs from the chippewa, tittabawassee, and saginaw river floodplains, midland, michigan, usa.	dietary exposure of house wrens (troglodytes aedon), tree swallows (tachycineta bicolor), and eastern bluebirds (sialia sialis) to polychlorinated dibenzofurans (pcdfs) and polychlorinated dibenzo-p-dioxins (pcdds) near midland, michigan (usa) was evaluated based on site-specific data, including concentrations of residues in bolus samples and individual invertebrate orders and dietary compositions by study species. site-specific dietary compositions for the three species were similar to those re ...	2011	20145996
within seasons and among years: when are corticosterone levels repeatable?	hormones play a central role in integrating internal and external cues to help mediate life-history decisions as well as changes in behavior and physiology of individuals. describing the consistency of endocrine traits within and among individuals is an important step for understanding whether hormonal traits are dependable predictors of phenotypes that selection could act upon. however, few long-term field studies have investigated the individual consistency of hormonal traits. glucocorticoid h ...	2011	21872600
mercury in breeding saltmarsh sparrows (ammodramus caudacutus caudacutus).	environmental mercury exposure of birds through atmospheric deposition and watershed point-source contamination is an issue of increasing concern globally. the saltmarsh sparrow (ammodramus caudacutus) is of high conservation concern throughout its range and the potential threat of mercury exposure adds to other anthropogenic stressors, including sea level rise. to assess methylmercury exposure we sampled blood of the northern nominal subspecies of saltmarsh sparrows (a. c. caudacutus) nesting i ...	2011	21792662
Selenium accumulation and reproduction in birds breeding downstream of a uranium mill in northern Saskatchewan, Canada.	Selenium (Se) concentrations in aquatic invertebrates and bird eggs collected along the treated effluent receiving environment of the Key Lake uranium mill in northern Saskatchewan were significantly greater than from nearby reference areas, and in some cases (e.g., eggs of common loons-Gavia immer) were higher than commonly used thresholds for adverse reproductive effects in birds (i.e., 5 µg/g dry weight in diet; 12-15 µg/g dry weight in eggs). Mean Se concentrations in tree swallow (Tachycine ...	2011	21927945
consequences of immune system aging in nature: a study of immunosenescence costs in free-living tree swallows.	immunosenescence, the aging of the immune system, is well documented in humans and laboratory models and is known to increase infection risk, morbidity, and mortality among the old. immunosenescence patterns have recently been unveiled in various free-living populations, but their consequences in the wild have not been explored. we investigated the consequences of immunosenescence in free-living tree swallows tachycineta bicolor through a field experiment simulating a bacterial infection (challe ...	2011	21661557
the stress of parenthood? increased glucocorticoids in birds with experimentally enlarged broods.	variation in baseline glucocorticoid (cort) levels can be attributed, at least in part, to differences in energetic demands confronting individuals. elevated baseline cort levels are routinely interpreted as indicating individuals in poor condition, with low relative fitness. however, when greater reproductive effort increases energetic demands, individuals with high cort might paradoxically be those with the highest fitness. here, we experimentally test the hypothesis that increased reproductiv ...	2011	21632615
a test of the mismatch hypothesis: how is timing of reproduction related to food abundance in an aerial insectivore?	in seasonal environments, vertebrates are generally thought to time their reproduction so offspring are raised during the peak of food abundance. the mismatch hypothesis predicts that reproductive success is maximized when animals synchronize their reproduction with the food supply. understanding the mechanisms influencing the timing of reproduction has taken on new urgency as climate change is altering environmental conditions during reproduction, and there is concern that species will not be a ...	2011	21618924