Feather corticosterone levels on wintering grounds have no carry-over effects on breeding among three populations of great skuas (<i>Stercorarius skua</i>)

Environmental conditions encountered by migratory seabirds in their wintering areas can shape their fitness. However, the underlying physiological mechanisms remain largely unknown as birds are relatively inaccessible during winter. To assess physiological condition during this period, we measured corticosterone concentrations in winter-grown primary feathers of female great skuas (Stercorarius skua) from three breeding colonies (Bjørnøya, Iceland, Shetland) with wintering areas identified from characteristic stable isotope signatures. We subsequently compared winter feather corticosterone levels between three wintering areas (Africa, Europe and America). Among females breeding in 2009, we found significant differences in feather corticosterone levels between wintering areas. Surprisingly, levels were significantly higher in Africa despite seemingly better local ecological factors (based on lower foraging effort). Moreover, contrary to our predictions, females sharing the same wintering grounds showed significant differences in feather corticosterone levels depending on their colony of origin suggesting that some skuas could be using suboptimal wintering areas. Among females wintering in Africa, Shetland females showed feather corticosterone levels on average 22% lower than Bjørnøya and Iceland females. Finally, the lack of significant relationships between winter feather corticosterone levels and any of the breeding phenology traits does not support the hypothesis of potential carry-over effects of winter feather corticosterone. Yet, the fitness consequences of elevated feather corticosterone levels remain to be determined

Dairy wintering systems in southern New Zealand : quantification and modelling of nutrient transfers and losses from contrasting wintering systems : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Palmerston North, New Zealand

Traditional dairy wintering practice in the lower South Island of New Zealand has been to graze brassica crops in situ. This practice has been under increasing scrutiny from local Regional Councils due to the relatively high nitrogen (N) leaching losses from this component of the whole farm system. Alternative wintering options to reduce N leaching losses that are currently available to farmers (such as barns and permanent wintering pads) are high cost and involve a large capital investment. In this work a new wintering system (termed a ‘portable pad’) was developed for use on support blocks (which can be located many kilometres from the milking platform) as an interim measure for reducing N leaching losses that is low cost and low input. This system is designed as a mitigation strategy that is available for use immediately while research investigates more permanent solutions. This system is a hybrid of the traditional crop grazing system and an off-paddock system, where effluent is captured. It makes use of the advantages of each of the original systems utilising the low cost feed source of the brassica crops, grazed in situ, while also utilising the benefits of duration controlled grazing with its associated effluent capture and irrigation at low rates. The aim of the research was to generate whole system N leaching loss values for each of the three farm systems investigated (crop wintering, deep-litter wintering barn, and portable pad). Field and laboratory research was conducted to fill identified knowledge gaps such that system N loss values could be estimated. OVERSEER Nutrient Budget software tool was used in conjunction with measured and modelled (APSIM) data to simulate whole farm N leaching loss values for the three farm systems investigated. Nitrogen leaching losses from the portable pad and barn systems were between 5 and 26 % and between 13 and 26 % lower, respectively, than the crop wintering system

Provenance does matter: links between winter trophic segregation and the migratory origins of European robins

Amongst migratory species, it is common to find individuals from different populations or geographical origins sharing staging or wintering areas. Given their differing life histories, ecological theory would predict that the different groups of individuals should exhibit some level of niche segregation. This has rarely been investigated because of the difficulty in assigning migrating individuals to breeding areas. Here, we start by documenting a broad geographical gradient of hydrogen isotopes (δ2H) in robin Erithacus rubecula feathers across Europe. We then use δ2H, as well as wing-tip shape, as surrogates for broad migratory origin of birds wintering in Iberia, to investigate the ecological segregation of populations. Wintering robins of different sexes, ages and body sizes are known to segregate between habitats in Iberia. This has been attributed to the despotic exclusion of inferior competitors from the best patches by dominant individuals. We find no segregation between habitats in relation to δ2H in feathers, or to wing-tip shape, which suggests that no major asymmetries in competitive ability exist between migrant robins of different origins. Trophic level (inferred from nitrogen isotopes in blood) correlated both with δ2H in feathers and with wing-tip shape, showing that individuals from different geographic origins display a degree of ecological segregation in shared winter quarters. Isotopic mixing models indicate that wintering birds originating from more northerly populations consume more invertebrates. Our multi-scale study suggests that trophic-niche segregation may result from specializations (arising in the population-specific breeding areas) that are transported by the migrants into the shared wintering grounds

Year-round tracking of small trans-Saharan migrants using light-level geolocators

Since 1899 ringing (or banding) remained the most important source of information about migration routes, stopover sites and wintering grounds for birds that are too small to carry satellite-based tracking systems. Despite the large quantity of migrating birds ringed in their breeding areas in Europe, the number of ring recoveries from sub-Saharan Africa is very low and therefore the whereabouts of most small bird species outside the breeding season remain a mystery. With new miniaturized light-level geolocators it is now possible to look beyond the limits of ring recovery data. Here we show for the first time year round tracks of a near passerine trans-Saharan migrant, the European Hoopoe (Upupa epops epops). Three birds wintered in the Sahel zone of Western Africa where they remained stationary for most of the time. One bird chose a south-easterly route following the Italian peninsula. Birds from the same breeding population used different migration routes and wintering sites, suggesting a low level of migratory connectivity between breeding and wintering areas. Our tracking of a near passerine bird, the European Hoopoe, with light-level geolocators opens a new chapter in the research of Palaearctic-African bird migration as this new tool revolutionizes our ability to discover migration routes, stopover sites and wintering grounds of small birds

Winter Field Report, December 2015 to February 2016

As has been the trend in recent years, many species are lingering later in fall and even arriving earlier in spring. Along with lingering birds, mid-winter and overwintering records have increased. This winter was phenomenal in this respect, especially in that records were across the board in terms of species, suggesting that water conditions have moderated (more open water) and temperatures in general have also (passerines). Unprecedented records included first wintering White-winged Scoter and first Jan or Feb record of Orange-crowned Warbler. Second or third such records were set by Blue-winged Teal, Surf Scoter, Ruddy Duck, Eared Grebe, Greater Yellowlegs, Rock Wren, and Yellow-rumped (Audubon\u27s) Warbler. Late-lingering species were many, highlighted by record late Red-throated Loon, Pied-billed Grebe, and Least Sandpiper. Other noteworthy laggards were Red-necked Grebe, Double-crested Cormorant, Whooping Crane, Ruby-crowned Kinglet, Hermit Thrush, Rose-breasted Grosbeak, Savannah Sparrow, Lincoln\u27s Sparrow, and Dickcissel, while Eastern Bluebirds set a new CBC high and Yellow-rumped Warblers were present through winter in almost unprecedented numbers (see last winter). Early spring arrivals are usually determined by factors other than local Nebraska environmental conditions, and so are perhaps less variable; nevertheless there were early-arriving Turkey Vulture, American Woodcock, and Franklin\u27s Gull. Perhaps the presence of these numerous winter phenomena allowed other species to winter farther north; there were no Herring Gulls reported 6-27 Jan, only 3 Red Crossbill reports were received, at least one of those of Pacific Coast Type 3 birds, and very few Townsend\u27s Solitaires were counted. Perhaps the only species that was unexpectedly low in numbers given these occurrences was Red-headed Woodpecker, virtually absent from the state, even at its winter stronghold, Indian Cave State Park. Additional significant numbers were a report of 10,000 American Robins, large numbers of Pine Siskins and American Goldfinches, and good numbers again of Yellow-bellied Sapsuckers. Interesting observations included an apparent shift eastward of wintering Brown Creepers, the still-parlous state of Black-billed Magpie in the state, now only in fair numbers in Keith and Scotts Bluff Cos. Eurasian Collared-Doves are abundant in the west, but in the east numbers are far lower, albeit increasing slowly. The third record of Barred Owl in Lincoln Co was of one in a large parking lot in North Platte; it was surmised that all three may have been hit by semis on 1-80 and transported there. As well as all of the winter excitement, there were several rarities detected, including one first state record. Unfortunately, it was Mute Swan, finally added to the state list based on numerous reports that have been difficult to pass off as escapees or released birds. In addition, Nebraska\u27s 7th Black-throated Sparrow appeared at the feeders of the Records Committee Chairman (I think it will be accepted), and there were rare sightings of Barrow\u27s Goldeneye in the east, near adult Kumlien\u27s Gull, Gyrfalcon, Common Raven (they like Applebee\u27s and Burger King), Varied Thrush, and Pine Grosbeak

High-resolution GPS tracking reveals sex differences in migratory behaviour and stopover habitat use in the lesser black-backed gull Larus fuscus

Sex-, size-or age-dependent variation in migration strategies in birds is generally expected to reflect differences in competitive abilities. Theoretical and empirical studies thereby focus on differences in wintering areas, by which individuals may benefit from avoiding food competition during winter or ensuring an early return and access to prime nesting sites in spring. Here, we use GPS tracking to assess sex-and size-related variation in the spatial behaviour of adult Lesser Black-backed Gulls (Larus fuscus) throughout their annual cycle. We did not find sex-or size-dependent differences in wintering area or the timing of spring migration. Instead, sexual differences occurred prior to, and during, autumn migration, when females strongly focussed on agricultural areas. Females exhibited a more protracted autumn migration strategy, hence spent more time on stopover sites and arrived 15 days later at their wintering areas, than males. This shift in habitat use and protracted autumn migration coincided with the timing of moult, which overlaps with chick rearing and migration. Our results suggest that this overlap between energy-demanding activities may lead females to perform a more prolonged autumn migration, which results in spatiotemporal differences in foraging habitat use between the sexes

Stable isotope ratios indicate that body condition in migrating passerines is influenced by winter habitat

Although predicted some time ago, there has been little success in demonstrating that the overall fitness of migratory birds depends on the combined influences of their experiences over all seasons. We used stable carbon isotope signatures (δ&lt;sup&gt;13&lt;/sup&gt;C) in the claws of migrating black-throated blue warblers &lt;i&gt;Dendroica caerulescens&lt;/i&gt; to infer their wintering habitats and investigated whether winter habitat selection can be linked to condition during migration. Resident bird species with low δ&lt;sup&gt;13&lt;/sup&gt;C corresponded to selection of more mesic habitats, and migrating birds with low δ&lt;sup&gt;13&lt;/sup&gt;C were in better condition than conspecifics with higher δ&lt;sup&gt;13&lt;/sup&gt;C signatures. These findings concur with empirical observations on the wintering grounds, where dominants (mostly males) tend to exclude subordinates from mesic areas (considered to be high-quality habitats). We believe that variation in condition during migration may be one of the key factors determining differences in arrival times and condition at the breeding areas, which in turn have a major influence on reproductive success

Long-term species richness-abundance dynamics in relation to species departures and arrivals in wintering urban bird assemblages

Temporal dynamics of local assemblages depend on the species richness and the total abundance of individuals as well as local departure and arrival rates of species. We used urban bird survey data collected from the same 31 study plots and methods during three winters (1991–1992; 1999–2000 and 2009–2010) to analyze the temporal relationship between bird species richness and total number of individuals (abundance). We also evaluated local departures and arrivals of species in each assemblage. In total, 13,812 individuals of 35 species were detected. The temporal variation in bird species richness followed the variation in the total number of individuals. The numbers of local departure and arrival events were similar. Also, the mean number of individuals of the recently arrived species (8.6) was almost the same as the mean number of individuals of the departed species (8.2). Risk of species departure was inversely related to number of individuals. Local species richness increased by one species when the total abundance of individuals increased by around 125 individuals and vice versa. Our results highlight the important role of local population departures and arrivals in determining the local species richness-abundance dynamics in human-dominated landscapes. Local species richness patterns depend on the total number of individuals as well as both the departure-arrival dynamics of individual species as well as the dynamics of all the species together. Our results support the more individuals hypothesis, which suggests that individual-rich assemblages have more species