Color of Artificial Light at Night Affects Incubation Behavior in the Great Tit, Parus major

Artificial light at night (ALAN) has been recognized as a biodiversity threat due to the drastic effects it can have on many organisms. In wild birds, artificial illumination alters many natural behaviors that are important for fitness, including chick provisioning. Although incubation is a key determinant of the early developmental environment, studies into the effects of ALAN on bird incubation behavior are lacking. We measured nest temperature in nest boxes of great tits during the incubation period in two consecutive years. Nest boxes were located in eight previously dark field sites that have been experimentally illuminated since 2012 with white, green, or red light, or were left dark. We tested if light treatment affected mean nest temperature, number of times birds leave the nest (off-bout frequency), and off-bout duration during the incubation period. Subsequently, we investigated if incubation behavior is related to fitness. We found that birds incubating in the white light during a cold, early spring had lower mean nest temperatures at the end of incubation, both during the day and during the night, compared to birds in the green light. Moreover, birds incubating in white light took fewer off-bouts, but off-bouts were on average longer. The opposite was true for birds breeding in the green light. Low incubation temperatures and few but long off-bouts can have severe consequences for developing embryos. In our study, eggs from birds that took on average few off-bouts needed more incubation days to hatch compared to eggs from birds that took many off-bouts. Nevertheless, we found no clear fitness effects of light treatment or incubation behavior on the number of hatchlings or hatchling weight. Our results add to the growing body of literature that shows that effects of ALAN can be subtle, can differ due to the spectral composition of light, and can be year-dependent. These subtle alterations of natural behaviors might not have severe fitness consequences in the short-term. However, in the long term they could add up, negatively affecting parent condition and survival as well as offspring recruitment, especially in urban environments where more environmental pollutants are present.

Comparative egg attendance patterns of incubating polar petrels

Background The internal environment of eggs in most birds is regulated by transferring heat energy through contact incubation, maintaining nest microclimate, and frequent egg turning by the incubating parent on its nest. However, we lack information about egg attendance patterns in birds that breed in polar environments where variations in life history are expected to influence incubation behavior. Moreover, crevice/burrow nesting petrels in high-latitude regions are known for periodically leaving their egg unattended (hereafter ‘egg neglect’), but there is little reporting on the internal condition of unattended eggs. At Dumont d’Urville Station, Antarctica, we studied the incubation behavior of 24 snow (Pagodroma nivea) and 15 Cape (Daption capense) petrel pairs using egg loggers that recorded egg turning rates, orientation changes, and temperatures at 1 Hz for durations of 3–6 days. Results Egg turning frequency (1.31 ± 0.33 vs. 1.38 ± 0.39 turns h−1), angle change per turn (43.1 ± 43.2 vs. 48.6 ± 43.7° turn−1), and egg temperature (34.1 ± 2.3 vs. 34.1 ± 2.0 °C) were nearly identical for snow and Cape petrels, respectively. However, egg neglect was only observed in snow petrel nests (based on egg temperature changes) where loggers recorded mean durations of 1.34 ± 1.15 days (maximum duration of 3.63 days). During periods of neglect, eggs cooled to 5.5 ± 1.8 °C over an average of 91 min, but were rewarmed by parents in only 76 min at a rate of 0.33 °C min−1. Conclusions Egg temperatures of both species during regular incubation were within 1–2 °C of other high-latitude petrel species, but neglected snow petrel eggs remained several degrees above freezing, which was likely attributed to crevice nesting where neglected eggs are buffered by environmental conditions. Using egg rewarming rates, thermal capacity of eggs, and published metabolic rates, we estimate egg rewarming costs in snow petrels to be 1.5 to 1.9 × BMR. Excluding egg neglect periods, turning rates for both petrel species were lower than other seabirds studied using biologging devices, which may be associated with the prolonged incubation periods that are characteristic of procellariiform seabirds.

Incubation Behavior Differences in Urban and Rural House Wrens, Troglodytes aedon

As global land surfaces are being converted to urban areas at an alarming rate, understanding how individuals respond to urbanization is a key focus for behavioral ecology. As a critical component of avian parental care, incubating adults face a tradeoff between maintaining an optimal thermal environment for the developing embryos while meeting their own energetic demands. Urban habitats are biotically and abiotically different from their rural counterparts, i.e., in food availability, predator compositions, and the thermal environment. Therefore, urban birds may face different incubation challenges than their natural counterparts. We measured incubation behavior of rural and urban house wrens, Troglodytes aedon, with temperature loggers throughout the 12-day period. We found that urban females had more incubation bouts of shorter duration and spent less total time incubating per day than rural females. Results could provide evidence of behavioral shifts of wrens in cities, which have implications for the evolution of parental care. Our findings contribute to our understanding of the behavioral traits needed for city life and possible environmental pressures driving urban adaptations.

Phenological Mismatch is Correlated with Fitness Outcomes and Adaptive Behavior in a Generalist Avian Predator Distributed Across North America

Climate-driven advances in the start of spring may result in a phenological mismatch between peak-prey abundance and the breeding season of secondary consumers. Phenological mismatch has been well-studied in insectivorous birds for which reproductive productivity is strongly linked to caterpillar abundance. The effects of mismatch on the productivity of dietary generalists, that forage on several types of prey, are less well-understood. Further, few studies have addressed questions about the effects of mismatch on survival, an important component of fitness that can be affected by breeding in sub-optimal conditions. We examined the relationship between phenological mismatch and fitness for a widespread generalist raptor, the American kestrel (Falco sparverius). In the first chapter, we collected productivity data from nest observations across the contiguous US and southern Canada and quantified phenological mismatch on each nest as the difference in days between the start of spring and clutch initiation. Then, we examined the relationship between mismatch, location, and productivity. Also, we investigated whether incubation behavior leading to hatching-asynchrony was related to phenological mismatch. Kestrels that laid eggs after the start of spring had fewer nestlings and higher rates of nest failure compared to kestrels that laid eggs before the start of spring. The strength of the mismatch effect depended on location. In the northeast, the number of fledglings per brood and rates of nest success were high for pairs nesting before the start of spring, but the effect of phenological mismatch was strongest here, with rapid declines in nest success associated with mismatch. Whereas, in the xi southwest, early-laying pairs had lower productivity and success relative to the northeast, but the effects of phenological mismatch were not as strong as the northeast. The effect of location is likely related to climatic constraints on the growing season and the time window for kestrel breeding that are becoming stronger in the northeast and weaker in the southwest. The timing of male incubation behavior was associated with hatching asynchrony, and males breeding after the start of spring were more likely to initiate incubation early as opposed to males breeding before the spring index date, suggesting that hatching asynchrony is a possible mechanism to cope with phenological mismatch. In the second chapter, we investigated the relationships between phenological mismatch and survival using mark-and-recapture data from two distinct, long-term study sites in Idaho and New Jersey where kestrel exhibit difference migration strategies. We created a multistate mark-recapture models to estimate the annual survival of adult (afterhatch- year) and juvenile (hatch-year or yearling) kestrels. For the multistate framework, we categorized the phenological mismatch of nests at each site “earlier” or “later” relative to the yearly median difference in days between clutch initiation date and the start-of-spring date, which was estimated at each nest box location. In addition, we included covariates for nesting success, sex, and minimum winter temperature anomaly in our survival models. Mismatch was associated with the survival of kestrels that produced young; however, the direction of this effect differed between populations. In Idaho, successful kestrels had higher survival when they bred “earlier” rather than “later.” In New Jersey, successful kestrels had higher survival when they bred “later” rather than “earlier." Differences in survival between sites may reflect differences in seasonality, climate change patterns, or consequences of migration strategies. For partially migrant xii populations (i.e, Idaho kestrels), mismatch may rapidly drive directional selection for birds to breed earlier by favoring survival and productivity, but for fully migrant populations (i.e., New Jersey) that have a limited window of time to reproduce, mismatch may create trade-offs between reproduction and survival. Mismatch did not affect the survival of adult birds with failed nests, and there was no difference in survival between hatch-year birds produced from “earlier” or “later” nests. In Idaho, males had higher survival rates than females and warmer winter temperatures positively correlated with survival in all age and sex classes. In New Jersey, sex and winter temperature did not explain survival. In sum, we found negative consequences of phenological mismatch on the fitness of American kestrels, generalist predator. For both productivity and survival, the effect of mismatch was more severe for kestrels in the northeast, where the breeding season is shorter and kestrels more migratory when compared to the west. These results demonstrate that duration of breeding season is an important factor to consider when assessing vulnerability to climate change, and that a generalist diet does not ensure resilience to phenological mismatch.