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Item Global flyway evolution in red knots Calidris canutus and genetic evidence for a Nearctic refugium(John Wiley and Sons, Ltd, 2022-04) Conklin JR; Verkuil YI; Battley PF; Hassell CJ; ten Horn J; Johnson JA; Tomkovich PS; Baker AJ; Piersma T; Fontaine MC; qu YPresent-day ecology and population structure are the legacies of past climate and habitat perturbations, and this is particularly true for species that are widely distributed at high latitudes. The red knot, Calidris canutus, is an arctic-breeding, long-distance migratory shorebird with six recognized subspecies defined by differences in morphology, migration behavior, and annual cycle phenology, in a global distribution thought to have arisen just since the last glacial maximum (LGM). We used nextRAD sequencing of 10,881 single-nucleotide polymorphisms (SNPs) to assess the neutral genetic structure and phylogeographic history of 172 red knots representing all known global breeding populations. Using population genetics approaches, including model-based scenario-testing in an approximate Bayesian computation (ABC) framework, we infer that red knots derive from two main lineages that diverged ca. 34,000 years ago, and thus most probably persisted at the LGM in both Palearctic and Nearctic refugia, followed by at least two instances of secondary contact and admixture. Within two Beringian subspecies (C. c. roselaari and rogersi), we detected previously unknown genetic structure among sub-populations sharing a migratory flyway, reflecting additional complexity in the phylogeographic history of the region. Conversely, we found very weak genetic differentiation between two Nearctic populations (rufa and islandica) with clearly divergent migratory phenotypes and little or no apparent contact throughout the annual cycle. Together, these results suggest that relative gene flow among migratory populations reflects a complex interplay of historical, geographical, and ecological factors.Item Ecology of migrant shorebirds in New Zealand, focussing on Farewell Spit, north-west Nelson : a thesis presented in partial fulfilment of the requirements for the degree of Masterate in Ecology at Massey University(Massey University, 1996) Battley, Phil F. (Philip Frank)Migratory shorebirds are a dynamic component of New Zealand's coastal fauna, alternating between distant breeding and non-breeding grounds. The Red Knot Calidris canutus, Bar-tailed Godwit Limosa lapponica and Pied Oystercatcher Haematopus ostralegus finschi were studied on Farewell Spit, North-West Nelson. The first two species breed in the Arctic and migrate to New Zealand for the non-breeding season. Over the southern summer they experience low thermostatic costs and generally improving prey conditions over the summer. Oystercatchers are resident over autumn and winter, so experience rising costs and declining prey quality in some species. One bivalve species, Macomona liliana, shows seasonal depth changes in the sediment, and so is largely inaccessible even to a long-billed bird such as the oystercatcher. Despite this, oystercatchers feed for less time than is available, and achieve intake rates sufficient to cover estimated needs. The energy needs of the Arctic waders rise as they prepare to migrate, and they achieve at least part of this by increasing the duration of feeding. Knots during spring tides in the premigratory period feed for the entire low-water period. Godwits are apparently less stressed, underutilising nocturnal feeding opportunities over summer. They are thought to increase feeding time by using this night-time feeding. The high energy demands for migrating birds come from the need to deposit nutrients for migration, and knots around the Auckland region are estimated to increase in mass from 115 to 185 g prior to migration. Fat deposition is not the only physiological preparation, however, and a sample of knots shot from Northland (illegally, recovered by DoC) revealed complex interactions between organs. Large amounts of fat were deposited, mostly in a subcutaneous layer but also in the abdominal cavity. Muscle protein was also deposited in flight and heart muscles, presumably to prepare for the extreme effort involved in trans-oceanic flights. At the same time, digestive organs decreased in mass. This is interpreted as freeing up muscle protein which is then deposited in organs for use during flight. Knots and godwits migrated from Farewell Spit in March. Most departures occurred in the evening and on rising tides. The former probably allows for the use of multiple navigational cues, while the latter may maximise feeding opportunities immediately before the flight. Most departures occurred after the passage of a low-pressure system or with the approach of a high-pressure system. This enabled favourable winds to be gained, so that the mean wind vector was a small tailwind. Thus, while departure directions were intermediate between the expected directions for flights to either Australia or northern New Zealand, it is probable they were able to fly across the top of a high-pressure system and gain wind assistance for a direct flight to Australia. However, the variability in flight range estimates depending on assumptions of travel-speed and protein deposition makes predicting migration routes difficult. Numbers of godwits have increased on Farewell Spit over the past decade, while oystercatchers have remained static Knots have shown a slight decline. Knot numbers are independent of national census counts so are presumably determined largely by factors operating on Farewell Spit itself. A possible mechanism that could give to a slowly declining population could be if a certain sector of the population fails to deposit sufficient nutrients to successfully migrate and return. If site-fidelity is very high (as it generally is in waders) then a long-term decrease could ensue.Item Extreme migration and the annual cycle : individual strategies in New Zealand Bar-tailed Godwits : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Palmerston North, New Zealand(Massey University, 2011) Conklin, Jesse RayLong-distance migration places severe constraints on the annual cycles of birds, as they balance the energetic and scheduling requirements of breeding, moult, pre-migratory fuelling, and the journey itself. The most extreme migrations, traversing vast, inhospitable areas of the globe in protracted non-stop flights, may push birds to the limits of their capabilities, and would be expected to tolerate little variation in performance. Despite this, Bar-tailed Godwits Limosa lapponia baueri, which are among the world’s greatest endurance migrants, embark on northward migration from New Zealand across a month-long period, and individuals are quite faithful to their particular schedules. Godwits are highly sexually dimorphic in plumage and body size, and there is additionally substantial individual variation within each sex in both traits. These patterns demonstrate a surprising diversity of strategies within a system that should contain little room for error. In this thesis, I sought to identify the roots and consequences of both persistent and ephemeral individual differences in migration and moult of New Zealand Bar-tailed Godwits, and to identify constraints and potential bottlenecks in their annual cycle. To do this, I combined a fine-resolution multi-year focus on individuals and an entire annual-cycle perspective, both of which have generally been impossible in studies of long-distance migratory birds. At a single non-breeding site, I closely monitored moult and migration of individual Bar-tailed Godwits for three non-breeding seasons, and linked these with events outside of New Zealand by tracking a subset of the same individuals on their complete migrations to Alaska breeding grounds and back. I supplemented this by travelling to Alaska myself and describing how godwits are distributed by size and plumage across their vast breeding range. I found that most of the variation among individual Bar-tailed Godwits was linked to where they nested in Alaska: within each sex, northerly breeders were smaller, had more extensive breeding plumage, and migrated later on both northbound and southbound migrations. The differences in migration timing can be explained by variation in when tundra breeding sites become snow-free and available across a latitudinal gradient, but reasons for geographic differences in plumage and size are less clear. Variation in breeding plumage was associated with different strategies for scheduling moult, both in New Zealand and during northbound migratory stopover in the Yellow Sea. Individual godwits were extraordinarily consistent between years in their timing of departure from New Zealand, and most ‘off-schedule’ departures were attributable to birds avoiding unfavourable winds for migration. Surprisingly, timing of arrival in New Zealand after the longest recorded non-stop flight did not appear to influence a godwit’s ability to prepare for its next migration, as timing of subsequent migratory departure and extent of breeding plumage on departure were both unaffected and very consistent. Across the entire year, scheduling of events became more precisely timed as the breeding season approached, but movements were generally much more tightly scheduled than moults. These findings show that Bar-tailed Godwits adopt and enact an array of individualised strategies within an apparently constrained system. The inter-relationships among events in different parts of the globe show that an individual-based, full annual-cycle perspective is required to understand patterns in any particular season. The consistent manner in which godwits conduct their annual routines, while still demonstrating flexibility to address unforeseen circumstances, challenges us to reconsider the view of extreme long-distance migrants as organisms operating at the limits of their capabilities.