| counting on your friends: the role of social environment on quantity discrimination. | quantity discrimination has been established in a range of species. however, most demonstrations of quantity discrimination control for social factors by testing animals individually. i tested whether sociality affects quantity discrimination in the wild by comparing the performances of the highly social mexican jay (mj; aphelocoma wollweberi) and the territorial western scrub jay (wj; aphelocoma californica). the birds were given a choice between two lines of peanuts that differed in initial qu ... | 2016 | 27036232 |
| speciation in the highlands of mexico: genetic and phenotypic divergence in the mexican jay (aphelocoma ultramarina). | the pine-oak woodlands of the mexican highlands harbour significant biological diversity, yet little is known about the evolutionary history of organisms inhabiting this region. we assessed genetic and phenotypic differentiation in 482 individuals representing 27 populations of the mexican jay (aphelocoma ultramarina) - a widespread bird species of the mexican highlands - to test whether populations in the central and northern mexican sierras display discrete breaks between groups, which would b ... | 2008 | 18430143 |
| geographic variation in mexican jays (aphelocoma ultramarina): local differentiation, polyphyly or hybridization? | studies of genetic variation within highly variable taxa can provide valuable insight into the factors influencing biological diversification. we examined six microsatellite loci, a nuclear intron and the mitochondrial control region to determine if the mexican jay subspecies aphelocoma ultramarina couchii and a. u. potosina have hybridized with western scrub-jays (a. californica). we suspected hybridization because these mexican jay populations resemble scrub-jays in several traits. we sampled ... | 2004 | 15315684 |
| differences in hippocampal volume among food storing corvids. | the hippocampal complex (hippocampus and parahippocampalis) is known to play a role in spatial memory in birds and is known to be larger in food-storing versus non-storing birds. in the present study, we investigated the relative volume of the hippocampal complex in four food-storing corvids: gray-breasted jays (aphelocoma ultramarina), scrub jays (aphelocoma coerulescens), pinyon jays (gymnorhinus cyanocephalus), and clark's nutcrackers (nucifraga columbiana). the results show that clark's nutc ... | 1996 | 8680849 |
| niche expansion leads to small-scale adaptive divergence along an elevation gradient in a medium-sized passerine bird. | niche expansion can lead to adaptive differentiation and speciation, but there are few examples from contemporary niche expansions about how this process is initiated. we assess the consequences of a niche expansion by mexican jays (aphelocoma ultramarina) along an elevation gradient. we predicted that jays at high elevation would have straighter bills adapted to feeding on pine cones, whereas jays at low elevation would have hooked bills adapted to feeding on acorns. we measured morphological a ... | 2008 | 18544512 |
| integrating paleoecology and genetics of bird populations in two sky island archipelagos. | genetic tests of paleoecological hypotheses have been rare, partly because recent genetic divergence is difficult to detect and time. according to fossil plant data, continuous woodland in the southwestern usa and northern mexico became fragmented during the last 10,000 years, as warming caused cool-adapted species to retreat to high elevations. most genetic studies of resulting 'sky islands' have either failed to detect recent divergence or have found discordant evidence for ancient divergence. ... | 2008 | 18588695 |
| isolation of tetranucleotide microsatellites from the mexican jay aphelocoma ultramarina. | | 1997 | 9161019 |
| effects of vasoactive intestinal peptide on prolactin secretion in three species of passerine birds. | previous work on domesticated species has indicated that vasoactive intestinal peptide (vip) is an important prolactin-releasing factor in these birds, but no comparative work in passerine birds has been reported. this study showed that iv injections of vip (50-100 microg/kg body mass) result in a dramatic, but transitory, rise in plasma prolactin in mexican jays (aphelocoma ultramarina). significant increases in prolactin were also observed following vip injection in blue jays (cyanocitta crist ... | 1999 | 9882553 |
| long-term trend toward earlier breeding in an american bird: a response to global warming? | in regions with severe winters, global warming may be expected to cause earlier onset of breeding in most animals, yet no documentation of such a trend exists in north america. in a study of marked individuals of the mexican jay (aphelocoma ultramarina) in southeastern arizona, from 1971 to 1998, the mean julian date of first clutch in the population declined significantly by 10.1 days. the date of the first nest in the population also became earlier, by 10.8 days. these changes were associated ... | 1999 | 10318924 |
| high frequency of extrapair fertilization in a plural breeding bird, the mexican jay, revealed by dna microsatellites. | we used tetra-nucleotide microsatellite dna typing to estimate the frequency of extrapair fertilization (epf) in a plural breeding species, the mexican jay, aphelocoma ultramarina, in arizona. we found epf in 32 of 51 complete broods (63%) and 55 of 139 nestlings (40%) for which the putative father had been identified (one of the highest rates of epf known for birds). at least 96.1% of epf fathers came from within the group. this is by far the highest known within-group epf rate among socially m ... | 2000 | 11124886 |
| does niche divergence accompany allopatric divergence in aphelocoma jays as predicted under ecological speciation? insights from tests with niche models. | the role of ecology in the origin of species has been the subject of long-standing interest to evolutionary biologists. new sources of spatially explicit ecological data allow for large-scale tests of whether speciation is associated with niche divergence or whether closely related species tend to be similar ecologically (niche conservatism). because of the confounding effects of spatial autocorrelation of environmental variables, we generate null expectations for niche divergence for both an ec ... | 2010 | 19922442 |