| brueelia (phthiraptera: ischnocera: philopteridae) of north american nine-primaried oscines (aves: passeriformes: passerida) with descriptions of nine new species. | nine new species of chewing lice in the genus brueelia kéler, 1936 , are described from north american hosts. they are brueelia thorini n. sp. from haemorhous mexicanus frontalis (say, 1822) and haemorhous mexicanus potosinus griscom, 1928; brueelia straseviciusi n. sp. from haemorhous purpureus (gmelin, 1789); brueelia mattsonae n. sp. from coccothraustes vespertinus brooksi (grinnell, 1917); brueelia novemstriata n. sp. from icterus wagleri wagleri sclater, 1857, and i. parisorum bonaparte, 18 ... | 2019 | 31730417 |
| variation in chronotype is associated with migratory timing in a songbird. | like many organisms, birds exhibit daily (circadian) and seasonal biological rhythms, and within populations both daily and seasonal timing often vary among individuals. because photoperiod interacts with the circadian rhythms of many organisms to induce seasonal changes in behaviour and physiology, it is hypothesized that differences in daily timing, called chronotypes, underpin differences among individuals in the timing of seasonal events. for seasonal events stimulated by increasing daylengt ... | 2019 | 31455169 |
| declining food availability, corticosterone, and migratory response in a nomadic, irruptive migrant. | while obligate migrants time their movements to respond to predictable changes in the environment, facultative migration is characterized by more variable movements that are driven by unpredictable changes in resource availability. the proximate cues that trigger facultative migrations and the endocrine mechanisms involved in these responses remain poorly understood, though corticosterone may be a key mediator of facultative migration due to its effects on activity and metabolic processes. we co ... | 2019 | 30802442 |
| increasing photoperiod stimulates the initiation of spring migratory behaviour and physiology in a facultative migrant, the pine siskin. | the transition to a migratory state involves coordinated changes in physiology and behaviour. in species with regular, predictable (obligate) migrations, increasing day length triggers the expression of a spring migratory state and androgens play an important role in stimulating its development. by contrast, we know little about the environmental cues and endocrine mechanisms that regulate migration in species with less predictable (facultative) migrations. here, we tested whether photoperiod st ... | 2018 | 30225078 |
| non-photoperiodic regulation of reproductive physiology in the flexibly breeding pine siskin (spinus pinus). | in order to time reproduction to coincide with favorable conditions, animals use environmental cues to up- and down-regulate the reproductive axis appropriately. although photoperiodic cues are one of the best studied of such environmental cues, animals also attend to others such as temperature, food availability, rainfall and social cues. such non-photic cues are expected to be particularly important for tropical species and temperate-zone species that exhibit flexible or opportunistic breeding ... | 2012 | 22569115 |
| a potential mate influences reproductive development in female, but not male, pine siskins. | the role of photoperiod in avian reproductive timing has been well studied, and we are increasingly recognizing the roles of other environmental cues such as social cues. however, few studies have evaluated the extent to which males and females of the same species respond similarly to the same type of cue. moreover, previous studies have rarely examined how variation in the quality or nature of a given social cue might modulate its effect. here, we examine the sensitivity of male and female pine ... | 2016 | 26836771 |
| estrogen levels influence medullary bone quantity and density in female house finches and pine siskins. | medullary bone, a non-structural osseous tissue, serves as a temporary storage site for calcium that is needed for eggshell production in a number of avian species. previous research focusing primarily on domesticated species belonging to the anseriformes, galliformes, and columbiformes has indicated that rising estrogen levels are a key signal stimulating medullary bone formation; passeriformes (which constitute over half of extant bird species and are generally small) have received little atte ... | 2017 | 28039066 |