Leo W. Bruinzeel

LOCAL DOMINANCE AND TERRITORIAL SETTLEMENT OF NONBREEDING OYSTERCATCHERS

1. We studied the mechanisms of territory acquisition in an oystercatcher (Haematopus ostralegus) breeding population on Schiermonnikoog (1983-1997), competing for low quality (leapfrog) and high quality (resident) territories. 2. Numbers of nonbreeders o

Wild Bird Movements and Avian Influenza Risk Mapping in Southern Africa

Global analyses of the potential for avian influenza transmission by wild birds have ignored key characteristics of the southern African avifauna. Although southern Africa hosts a variety of migratory, Holarctic-breeding wading birds and shorebirds, the documented prevalence of avian influenza in these species is low. The primary natural carriers of influenza viruses in the northern hemisphere are the anatids, i.e., ducks. In contrast to Palearctic-breeding species, most southern African anatids do not undertake predictable annual migrations and do not follow migratory flyways. Here we present a simple, spatially explicit risk analysis for avian influenza transmission by wild ducks in southern Africa. We developed a risk value for each of 16 southern African anatid species and summed risk estimates at a quarter-degree cell resolution for the entire subregion using data from the Southern African Bird Atlas. We then quantified environmental risks for South Africa at the same resolution. Combining these two risk values produced a simple risk map for avian influenza in South Africa, based on the best currently available data. The areas with the highest risk values were those near the two largest cities, Johannesburg and Cape Town, although parts of Kwazulu-Natal and the Eastern Cape also had high-risk scores. Our approach is simple, but has the virtue that it could be readily applied in other relatively low-data areas in which similar assessments are needed; and it provides a first quantitative assessment for decision makers in the subregion.

Energetic Demands During Incubation and Chick Rearing in a Uniparental and a Biparental Shorebird Breeding in the High Arctic

ABSTRACT.— Rearing of young has long been considered the energetically most demanding phase of the avian breeding cycle. Arctic-breeding shorebirds expend large amounts of energy during breeding. Because they are too small to carry sufficient stores to sit out the incubation period, they regularly interrupt incubation to feed and still can run short of energy, particularly in species in which one adult takes care of the eggs and chicks alone (uniparental). We measured daily energy expenditure (DEE) and time budgets during incubation and chick rearing in the smallest uniparental Arctic shorebird, the Little Stint (Calidris minuta). Daily energy expenditure decreased with increasing temperature but did not differ between the incubation and chick-rearing periods. Because of the increase in potential foraging time from incubation to the chick-rearing phase, the foraging intake rate required to balance the budget dropped by two-thirds. To evaluate the effect of uniparental care on energy budgets, we also measured DEE in the Dunlin (C. alpina), a sympatric congener in which both parents incubate but the female deserts the brood after hatching. Daily energy expenditure decreased with temperature, was the same during incubation and chick rearing, and was higher in males. Our results are discussed in relation to the timing of breeding of Arctic shorebirds with different systems of parental care.

Post-Breeding Migration of Dutch-Breeding Black-Tailed Godwits: Timing, Routes, Use of Stopovers, and Nonbreeding Destinations

Conservation of long-distance migratory shorebirds is complex because these species use habitats spread across continents and hemispheres, making identification of critical habitats and potential bottlenecks in the annual cycle especially difficult. The population of Black-tailed Godwits that breeds in Western Europe, Limosa limosa limosa, has declined precipitously over the past few decades. Despite significant efforts to identify the root causes of this decline, much remains unclear. To better understand the migratory timing, use of stopover and nonbreeding sites, and the potential impact of breeding success on these parameters, we attached 15 Argos satellite transmitters and 10 geolocation tracking devices to adult godwits nearing completion of incubation at breeding sites in southwest Friesland, The Netherlands during the spring of 2009. We successfully tracked 16 adult godwits for their entire southward migration and two others for part of it. Three migration patterns and four regions of use were apparent. Most godwits left their breeding sites and proceeded south directly to stopover sites in the Mediterranean — e.g. Spain, Portugal, and Morocco — before flying on to non-breeding sites in West Africa. Other individuals spent the entire nonbreeding season in the Mediterranean. A third pattern included a few individuals that flew nonstop from their Dutch breeding sites to nonbreeding sites in West Africa. Tracking data from this study will be immediately useful for conservation efforts focused on preserving the dispersed network of sites used by godwits during their southward migration.

Competitive abilities of oystercatchers (Haematopus ostralegus) occupying territories of different quality

In territorial species, habitat heterogeneity results in some individuals occupying poor quality sites while others occupy high quality sites. Floaters (mature nonbreeders) may accept a low quality territory, because it is the best they can get and defend (‘inferior phenotype hypothesis’), or because it is a strategic alternative for a high quality territory in the long run (‘queue hypothesis’). Oystercatcher Haematopus ostralegus territories differ consistently in the amount of offspring produced each year and this is related to the distance between the nesting and feeding territories. The inferior phenotype hypothesis was previously rejected on the basis of the absence of morphometric differences (assumed to indicate competitive abilities) among breeders. We investigated social dominance, in the field and in captivity, in relation to the quality of the breeding territory. In the field, birds with high-quality territories won more often compared to those occupying low-quality territories. However, this difference was not apparent in a small dataset of captive birds. These results are discussed in the framework of the long-term fitness prospects of settling in a high or low quality territory.