In an investigation of the factors leading to geographic structuring among Adélie Penguin (Pygoscelis adeliae) populations, we studied the size and overlap of colony‐ specific foraging areas within an isolated cluster of colonies. The study area, in the southwestern Ross Sea, included one large and three smaller colonies, ranging in size from 3900 to 135 000 nesting pairs, clustered on Ross and Beaufort Islands. We used triangulation of radio signals from transmitters attached to breeding penguins to determine foraging locations and to define colony‐specific foraging areas during the chick‐provisioning period of four breeding seasons, 1997–2000. Colony populations (nesting pairs) were determined using aerial photography just after egg‐laying; reproductive success was estimated by comparing ground counts of chicks fledged to the number of breeding pairs apparent in aerial photos. Foraging‐trip duration, meal size, and adult body mass were estimated using RFID (radio frequency identification) tags and an automated reader and weighbridge. Chick growth was assessed by weekly weighing. We related the following variables to colony size: foraging distance, area, and duration; reproductive success; chick meal size and growth rate; and seasonal variation in adult body mass. We found that penguins foraged closest to their respective colonies, particularly at the smaller colonies. However, as the season progressed, foraging distance, duration, and area increased noticeably, especially at the largest colony. The foraging areas of the smaller colonies overlapped broadly, but very little foraging area overlap existed between the large colony and the smaller colonies, even though the foraging area of the large colony was well within range of the smaller colonies. Instead, the foraging areas of the smaller colonies shifted as that of the large colony grew. Colony size was not related to chick meal size, chick growth, or parental body mass. This differed from the year previous to the study, when foraging trips of the large colony were very long, parents lost mass, and chick meals were smaller. In light of existing data on prey abundance in neritic waters in Antarctica suggesting that krill are relatively evenly distributed and in high abundance in the Southern Ross Sea, we conclude that penguins depleted or changed the availability of their prey, that the degree of alteration was a function of colony size, and that the large colony affected the location (and perhaps ultimately the size) of foraging areas for the smaller colonies. It appears, therefore, that foraging dynamics play a role in the geographic structuring of colonies in this species.

Summary1. Nest predation limits avian fitness, so birds should favour nest sites that minimize predation risk. Nevertheless, preferred nest microhabitat features are often uncorrelated with apparent variation in predation rates. 2. This lack of congruence between theory-based expectation and empirical data may arise when birds already occupy 'adaptive peaks'. If birds nest exclusively in low-predation microhabitats, microhabitat and nest predation may no longer be correlated even though predation ultimately shaped microhabitat selection. 3. This 'adaptive peak hypothesis' was tested for a population of Yellow Warblers (Dendroica petechia) focusing on two nest microhabitat features: concealment and height. Experimental nests measured relative predation risk both within and outside the microhabitat range typically occupied by natural nests to examine whether nest site choices made by birds restricted our ability to detect microhabitat effects on predation. 4. Within the natural range (30-80% concealment, >75 cm height), microhabitat-predation relationships were weak and inconsistent, and similar for experimental and natural nests. Over an extended range, however, experimental predation rates were elevated in exposed sites (<30% concealed), indicating a concealment-related 'adaptive plateau'. 5. Clay egg bite data revealed a concealment effect on avian predators, and the abundance of one avian predator group correlated with nest concealment among years, suggesting these predators may cue birds to modulate nest concealment choices. 6. This study demonstrates how avian responses to predation pressure can obscure the adaptive significance of nest site selection, so predation influences may be more important than apparent from published data.

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Contrary to assumptions of habitat selection theory, fi eld studies frequently detect ' ecological traps ' , where animals prefer habitats conferring lower fi tness than available alternatives. Evidence for traps includes cases where birds prefer breeding habitats associated with relatively high nest predation rates despite the importance of nest survival to avian fi tness. Because birds select breeding habitat at multiple spatial scales, the processes underlying traps for birds are likely scale-dependent. We studied a potential ecological trap for a population of yellow warblers Dendroica petechia while paying specifi c attention to spatial scale. We quantifi ed nest microhabitat preference by comparing nest-versus random-site microhabitat structure and related preferred microhabitat features with nest survival. Over a nine-year study period and three study sites, we found a consistently negative relationship between preferred microhabitat patches and nest survival rates. Data from experimental nests described a similar relationship, corroborating the apparent positive relationship between preferred microhabitat and nest predation. As do other songbirds, yellow warblers select breeding habitat in at least two steps at two spatial scales; (1) they select territories at a coarser spatial scale and (2) nest microhabitats at a fi ner scale from within individual territories. By comparing nest versus random sites within territories, we showed that maladaptive nest microhabitat preferences arose during within-territory nest site selection (step 2). Furthermore, nest predation rates varied at a fi ne enough scale to provide individual yellow warblers with lower-predation alternatives to preferred microhabitats. Given these results, tradeoff s between nest survival and other fi tness components are unlikely since fi tness components other than nest survival are probably more relevant to territory-scale habitat selection. Instead, exchanges of individuals among populations facing diff erent predation regimes, the recent proliferation of the parasitic brown-headed cowbird Molothrus ater , and/or anthropogenic changes to riparian vegetation structure are more likely explanations.

Murine hydatid cysts of Echinococcus granulosus were incubated in vitro in the presence of nitric oxide produced from S-nitroso-N-acetylpenicillamine (SNAP) or interferon-gamma activated peritoneal macrophages. In both situations, evidence of cyst damage and death was observed by microscopy in over 77% of cysts after 3 days, indicating that intact hydatid cysts could be susceptible to a Th1 driven macrophage attack. A crude extract of the laminated layer from cysts was found to be able to reduce the production of nitric oxide from activated macrophages in vitro and in vivo and this may have been due to phagocytosis of laminated layer fragments by the macrophages. The results indicate that, although cysts may be susceptible to the effects of nitric oxide, the laminated layer may be involved in downregulating nitric oxide production.

Wood mice Apodemus sylvaticus were trapped each September over a 13-year period, from 1993 to 2005, in a wooded area adjacent to Malham Tarn, Yorkshire, UK. Plagiorchis muris was found to be the dominant intestinal trematode and occurred in every year of sampling, with an overall prevalence of 16.9%. This appears to be the first record of P. muris in A. sylvaticus within the UK. The mean worm burden was 2.03 and the distribution of the parasite within mice was typically overdispersed. No difference in prevalence relative to host sex was evident although there was a higher prevalence of 21.9% in larger older mice compared with 9.1% in juveniles, which probably relates to a greater foraging activity in older mice. Annual prevalence values of P. muris infections varied significantly over the study period with higher prevalences being associated with years with a high spring/summer rainfall. The second intermediate hosts for P. muris include a variety of aquatic insect larvae and it is likely that the higher rainfall may result in the occurrence of temporary water bodies suitable for the development of insect larvae.

A growing number of studies have looked at how climate change alters the effects of habitat fragmentation and degradation on both single and multiple species; some raise concern that biodiversity loss and its effects will be exacerbated. The published literature on spatial dynamics (such as dispersal and metapopulation dynamics), habitat fragmentation and climate change requires synthesis and a conceptual framework to simplify thinking. We propose a framework that integrates how climate change affects spatial population dynamics and the effects of habitat fragmentation in terms of: (i) habitat quality, quantity and distribution; (ii) habitat connectivity; and (iii) the dynamics of habitat itself. We use the framework to categorize existing autecological studies and investigate how each is affected by anthropogenic climate change. It is clear that a changing climate produces changes in the geographic distribution of climatic conditions, and the amount and quality of habitat. The most thorough published studies show how such changes impact metapopulation persistence, source-sink dynamics, changes in species' geographic range and community composition. Climate-related changes in movement behavior and quantity, quality and distribution of habitat have also produced empirical changes in habitat connectivity for some species. An underexplored area is how habitat dynamics that are driven by climatic processes will affect species that live in dynamic habitats. We end our discussion by suggesting ways to improve current attempts to integrate climate change, spatial population dynamics and habitat fragmentation effects, and suggest distinct areas of study that might provide opportunities for more fully integrative work

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