Marcela Liljesthröm

Clock gene variation in Tachycineta swallows.

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 between Clock poly-Q length polymorphism and latitude and, within a population, an association with the date of laying and the length of the incubation period. Despite relatively high overall breeding synchrony, the timing of clutch initiation has a large impact on the fitness of swallows in the genus Tachycineta. We compared length polymorphism in the Clock poly-Q region among five populations from five different Tachycineta species that breed across a hemisphere-wide latitudinal gradient (Fig. 1). Clock poly-Q variation was not associated with latitude; however, there was an association between Clock poly-Q allele diversity and the degree of clutch size decline within breeding seasons. We did not find evidence for an association between Clock poly-Q variation and date of clutch initiation in for any of the five Tachycineta species, nor did we found a relationship between incubation duration and Clock genotype. Thus, there is no general association between latitude, breeding phenology, and Clock polymorphism in this clade of closely related birds. Figure 1 Photos of Tachycineta swallows that were used in this study: A) T. bicolor from Ithaca, New York, B) T. leucorrhoa from Chascomús, Argentina, C) T. albilinea from Hill Bank, Belize, D) T. meyeni from Puerto Varas, Chile, and E) T. thalassina from Mono Lake, California, Photographers: B: Valentina Ferretti; A, C-E: David Winkler.

Chilean Swallows (Tachycineta meyeni) Adjust the Number of Feathers Added to the Nest with Time of Breeding

Abstract Tachycineta swallows nest in secondary cavities and build nests made of a mat of dry grasses with a nest cup lined with feathers. The insulative quality of feathers may prevent hypothermia of the chicks and increase chick growth, but also may raise the risk of nestling hyperthermia if ambient temperature is high. The number of feathers added to the nest should vary throughout the breeding season according to ambient temperature. We describe nest structure and timing of nest building of Chilean Swallows (Tachycineta meyeni) nesting in Tierra del Fuego, Argentina. We analyzed the association between number of feathers in the nest and (1) daily ambient temperature during the period swallows add feathers to the nest, and (2) hatching success of eggs and survival and growth of the chicks. There was a negative association between number of feathers added to the nest and average daily ambient temperature during the nesting cycle. Hatching success was not associated with number of feathers at start of laying or at the end of incubation. There was no association between number of feathers and chick survival or between number of feathers and average weight of the chicks when they were 12 and 15 days of age. Chilean Swallows make temporal adjustments to the number of feathers added to the nest. We suggest these adjustments may help maintain reproductive success throughout the breeding season.

Time of breeding and female condition affect chick-growth in the Chilean Swallow (Tachycineta meyeni)

Abstract We analysed growth of nestling Chilean Swallows (Tachycineta meyeni) over four consecutive breeding seasons and determined the factors that explain variation in growth rate, asymptotic body mass and length of the nestling period. As the breeding season advanced nestlings grew more slowly and attained lower asymptotic mass, but the length of the nestling period and nestling survival did not show any seasonal trend. Asymptotic body mass of nestlings increased with female body condition, which was negatively correlated with time of breeding, suggesting that a seasonal decline in asymptotic body mass could be the result of changes in environmental conditions or lower quality of females breeding later in the season. There was no relationship between average minimum ambient temperature and either growth rate or asymptotic mass during the nestlings first 10 days. However, short periods of poor weather and snowfall had a significant effect on nestling survival. Growth rate (0.43) was lower than that of other Tachycineta species nesting at similar latitudes in the northern hemisphere but similar to those of subtropical species of the genus, suggesting that the factors that have influenced the evolution of this life-history trait differ between Chilean Swallows and other species of Tachycineta.

Kelp Geese (Chloephaga hybrida) and Flightless Steamer-Ducks (Tachyeres pteneres) in the Beagle Channel: the importance of islands in providing nesting habitat

Abstract We describe the nest-site characteristics and breeding habitat use of Kelp Geese (Chloephaga hybrida) and Flightless Steamer-Ducks (Tachyeres pteneres) along 137 km of coastline on the northern shore of the Beagle Channel, Argentina, and 87 km of island coastline. We examined the importance of vegetation cover, predation, and tourism on the distribution of nests among islands. We found all nests only on islands and islets. Nesting sites for both species were strongly associated with higher proportions of high vegetation cover (shrubs). Kelp Geese were also associated with the absence of terrestrial predators. Tourist presence on islands was not associated with the occurrence of nests for either species. The northern coasts of the Beagle Channel and the islands and islets along the channel have similar habitat types. However, the islands and islets are relatively inaccessible to mammalian terrestrial predators compared to the coast of the channel where terrestrial predators are frequently recorded. Therefore, islands and islets seem to provide a relatively safe nesting habitat for Kelp Geese and Flightless Steamer-Ducks by offering refuge mainly from ground predators. Additionally, habitat changes caused by increased human disturbance along the northern shore of the Beagle Channel may also explain the presence of nests only on islands and islets, though further studies are needed to assess these effects. This study contributes new information on the breeding habitat and nesting sites of Flightless Steamer-Ducks and Kelp Geese in the Beagle Channel, to assist in the identification of priority breeding sites and habitats to protect. Also, it highlights the importance of islands and islets of the Beagle Channel as safe breeding refuge for these two ground nesting seabirds.

Nest Predators of Flightless Steamer-Ducks (Tachyeres pteneres) and Flying Steamer-Ducks (Tachyeres patachonicus)

Abstract. A combination of infrared cameras and plasticine eggs were used to identify potential nest predators of Flightless Steamer-Ducks (Tachyeres pteneres) and Flying Steamer-Ducks (T. patachonicus) and to evaluate the relative efficacy of these methods for identifying predators. Cameras were set up at 31 artificial nests with plasticine eggs and at four Flightless and two Flying steamer-duck nests. Two avian predators, Chimango Caracara (Milvago chimango) and Southern Crested Caracara (Caracara plancus), and two mammalian predators, Fuegian Culpeo fox (Pseudalopex culpaeus lycoides) and American mink (Neovison vison), were identified as depredating artificial nests from photos. Active Flightless and Flying steamer-duck nests were found only on islets, and from the photos the Chimango and Southern Crested caracaras were identified as nest predators. Mammalian predators were not photographed on islets (neither on artificial nor natural nests). Though the potential predator community at Lapataia Bay was small, there were considerable similarities in physical evidence and marks left at nests, especially within avian predators. Also, depredated nests were sometimes revisited by other predators and these multi-predator visits sometimes caused changes to the appearance of the depredated nest following departure of the initial predator. The cameras provided an objective method for definitive identification of nest predators.

Biparental nest-attendance in Chilean Swallows (Tachycineta meyeni) breeding in Ushuaia, Argentina

Abstract Intermittent female incubation, where eggs are left unattended periodically while the female forages, is common among passerines. In extremely cold environments, unattended eggs may be at risk of freezing or exposed to suboptimal developmental temperatures. Our aim was to examine incubation behaviour of Chilean Swallows nesting in a cold environment (daily average temperatures ~10°C) at the southern tip of Argentina, and the temperature regime of incubation. Females had bare, vascularised brood-patches, whereas males had false brood-patches, where feathering of the abdomen was somewhat sparse. Video-cameras were used at three nests, and at all three two adults were observed to attend eggs, day and night, confirming incubation by males. Temperature records of eggs showed that one adult (assumed to be the female) had high rates of attendance and maintained egg temperatures that approached 38–39°C when incubating, and the other adult (assumed male) had lower and variable rates of attendance and maintained egg temperatures generally above 34°C when incubating. The assumed female rarely left the eggs unless the assumed male was there to replace her. Researchers should be cautious when making conclusions using data from temperature loggers in situations where male attendance at nests during incubation is possible.