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Recent studies of several species have reported a latitudinal cline in the circadian clock gene, Clock, which influences rhythms in both physiology and behavior. Latitudinal variation in this gene may hence reflect local adaptation to seasonal variation. In some bird populations, there is also an among-individual association between Clock poly-Q genotype(More)
Many animals use photoperiod cues to synchronize reproduction with environmental conditions and thereby improve their reproductive success. The circadian clock, which creates endogenous behavioral and physiological rhythms typically entrained to photoperiod, is well characterized at the molecular level. Recent work provided evidence for an association(More)
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(More)
Telomerase is an enzyme capable of elongating telomeres, the caps at the ends of chromosomes associated with aging, lifespan and survival. We investigated tissue-level variation in telomerase across different ages in four bird species that vary widely in their life history. Telomerase activity in bone marrow may be associated with the rate of erythrocyte(More)
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.(More)
Across North America, tree swallows have advanced their mean date of clutch initiation (lay date) by approximately 9 days over the past 30 years, apparently in response to climate change. In a sample of 2,881 nest records collected by the lay public from 1959 to 1991, we examined whether clutch size has also responded to climate change. We found that clutch(More)
We studied whether polychlorinated biphenyls (PCBs) may alter the development of song control brain nuclei in zebra finch (Taeniopygia guttata) offspring of pulse-exposed hens. We orally administered 40 microg of Aroclor 1248 to adult female finches before egg laying. When the progeny were 50 d old, we measured the volumes of the song control nuclei(More)
Tree swallow (Tachycineta bicolor) breeding success in Ithaca, NY, USA, over the past quarter century has shown generally healthy fledgling production punctuated by years of high nestling mortality. This study tested the potential effects that temperature may have on the food supply and breeding success of swallows. Data from 17 years of daily insect(More)
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,(More)