Journal Articles
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Item Interacting Roles of Breeding Geography and Early-Life Settlement in Godwit Migration Timing(Frontiers Media SA, 17/03/2020) Battley PF; Conklin JR; Parody-Merino ÁM; Langlands PA; Southey I; Burns T; Melville DS; Schuckard R; Riegen AC; Potter MAWhile avian migration timing is clearly influenced by both breeding and non-breeding geography, it is challenging to identify the relative and interdependent roles of endogenous programs, early-life experience, and carry-over effects in the development of adult annual schedules. Bar-tailed godwits Limosa lapponica baueri migrate northward from New Zealand toward Asian stopover sites during the boreal spring, with differences in timing between individuals known to relate to their eventual breeding-ground geography in Alaska. Here, we studied the timing of northward migration of individual godwits at three sites spanning 1,100 km of New Zealand’s 1,400-km length. A lack of morphological or genetic structure among sites indicates that the Alaskan breeding population mixes freely across all sites, and larger birds (southern breeders) tended to migrate earlier than smaller birds (northern breeders) at all sites. However, we unexpectedly found that migration timing varied between the sites, with birds from southern New Zealand departing on average 9.4–11 days earlier than birds from more northerly sites, a difference consistent across 4 years of monitoring. There is no obvious adaptive reason for migration timing differences of this magnitude, and it is likely that geographic variation in timing within New Zealand represents a direct response to latitudinal variation in photoperiod. Using resightings of marked birds, we show that immature godwits explore widely around New Zealand before embarking on their first northward migration at age 2–4 years. Thus, the process by which individual migration dates are established appears to involve: (1) settlement by sub-adult godwits at non-breeding sites, to which they are highly faithful as adults; (2) a consequent response to environmental cues (i.e., photoperiod) that sets the local population’s migration window; and (3) endogenous mechanisms, driven by breeding geography, that establish and maintain the well-documented consistent differences between individuals. This implies that behavioral decisions by young godwits have long-lasting impacts on adult annual-cycle schedules, but the factors guiding non-breeding settlement are currently unknown.Item Effects of geolocators on hatching success, return rates, breeding movements, and change in body mass in 16 species of Arctic-breeding shorebirds.(2016) Weiser EL; Lanctot RB; Brown SC; Alves JA; Battley PF; Bentzen R; Bêty J; Bishop MA; Boldenow M; Bollache L; Casler B; Christie M; Coleman JT; Conklin JR; English WB; Gates HR; Gilg O; Giroux M-A; Gosbell K; Hassell C; Helmericks J; Johnson A; Katrínardóttir B; Koivula K; Kwon E; Lamarre J-F; Lang J; Lank DB; Lecomte N; Liebezeit J; Loverti V; McKinnon L; Minton C; Mizrahi D; Nol E; Pakanen V-M; Perz J; Porter R; Rausch J; Reneerkens J; Rönkä N; Saalfeld S; Senner N; Sittler B; Smith PA; Sowl K; Taylor A; Ward DH; Yezerinac S; Sandercock BKBACKGROUND: Geolocators are useful for tracking movements of long-distance migrants, but potential negative effects on birds have not been well studied. We tested for effects of geolocators (0.8-2.0 g total, representing 0.1-3.9 % of mean body mass) on 16 species of migratory shorebirds, including five species with 2-4 subspecies each for a total of 23 study taxa. Study species spanned a range of body sizes (26-1091 g) and eight genera, and were tagged at 23 breeding and eight nonbreeding sites. We compared breeding performance and return rates of birds with geolocators to control groups while controlling for potential confounding variables. RESULTS: We detected negative effects of tags for three small-bodied species. Geolocators reduced annual return rates for two of 23 taxa: by 63 % for semipalmated sandpipers and by 43 % for the arcticola subspecies of dunlin. High resighting effort for geolocator birds could have masked additional negative effects. Geolocators were more likely to negatively affect return rates if the total mass of geolocators and color markers was 2.5-5.8 % of body mass than if tags were 0.3-2.3 % of body mass. Carrying a geolocator reduced nest success by 42 % for semipalmated sandpipers and tripled the probability of partial clutch failure in semipalmated and western sandpipers. Geolocators mounted perpendicular to the leg on a flag had stronger negative effects on nest success than geolocators mounted parallel to the leg on a band. However, parallel-band geolocators were more likely to reduce return rates and cause injuries to the leg. No effects of geolocators were found on breeding movements or changes in body mass. Among-site variation in geolocator effect size was high, suggesting that local factors were important. CONCLUSIONS: Negative effects of geolocators occurred only for three of the smallest species in our dataset, but were substantial when present. Future studies could mitigate impacts of tags by reducing protruding parts and minimizing use of additional markers. Investigators could maximize recovery of tags by strategically deploying geolocators on males, previously marked individuals, and successful breeders, though targeting subsets of a population could bias the resulting migratory movement data in some species.Item Winter habitat use of New Zealand falcons (Falco novaeseelandiae ferox) in an intensively managed pine plantation, central North Island, New Zealand(New Zealand Ecological Society, 15/07/2017) Horikoshi C; Battley PF; Seaton R; Minot EODeforestation and conversion to intensive agriculture historically caused a large reduction in abundance of the New Zealand falcon, resulting in its current classification as At Risk. Many New Zealand falcons occur in managed plantation forests, but little is known about their winter use of the mosaic of different aged stands present in these forests. We radio tracked adult falcons (n = 36) during three winters (2012–2014) in Kaingaroa Forest, an intensively managed pine plantation located in the Central Plateau of the North Island of New Zealand. We used tracking data to establish the extent and habitat composition of winter home ranges, and transect surveys to assess the availability of potential prey (passerine birds). We also investigated whether falcon habitat use was related to weather. Open fields created by clearcutting were the primary hunting ground of falcons. Falcons occupied young pine stands (30.4%) and the ecotone between young and mature pine stands (31.2%) most frequently despite its limited availability (20.1% and 3.7%, respectively). Total prey abundance was similar across all habitats and sizes of open fields, but the species composition of potential prey differed significantly between habitats. Thus, the dynamic changes to forest structure created by clearcutting and its effects on prey accessibility are the most important factors influencing falcon space use. We observed that falcons used the mature portion of the forest edge area as a vantage point for hunting or for territorial defence and as a shelter from heavy rain, and interiors of mature tree stands as a shelter from strong winds. Females had larger home range size (95% KDE, 32 km2) than males (15 km2). The availability of mature/young edge within a home range may be the key factor determining home range size during winter. Maintaining the availability of ecotones of young stands adjacent to mature trees in plantation forests can assist in supporting falcon populations in this novel habitat and hence the conservation of this endemic raptor.