Publications

Interest in monitoring the population viability of the Brown Pelican (Pelecanus occidentalis) has recently risen in the context of the species’ 2009 delisting as endangered, rapid degradation of nesting habitat, and recent oil spills. To assess the Brown Pelican’s patterns of movement (across natal colony, nonnatal colony, and noncolony islands), age and sex structure, and survival probabilities, we banded 1177 chicks in Louisiana from 2007 to 2009. In band-resighting surveys within the Isles Dernieres archipelago from 2008 to 2010, we detected 92 of our banded birds. Neither age nor sex appeared to influence where we observed pelicans resting on beaches across the islands, and we found the highest proportions of pelicans at their natal island. Yet few observations of banded birds suggest either movement outside our study area or mortality. Conditions at colonies and proximity to other sites of loafing or colonies may in part explain the disparity in proportions of resightings of individuals banded on different islands. Finally, the apparent probability of survival of one-year-old pelicans was lower than that of two- and three-year olds. Insights into these trends in movement and survival of young Brown Pelicans can improve future management of colony sites.

Nesting colonies of coastal avifauna are perennially threatened by hurricanes, land loss, and environmental contamination. To understand how nest substrate and habitat availability influence reproductive success of Brown Pelicans (Pelecanus occidentalis), we monitored 802 nests and quantified vegetation cover on two barrier islands in Louisiana from 2008 to 2010. In 2008, Hurricanes Gustav and Ike caused habitat degradation and land loss at our study sites and thus allowed comparison of pelican productivity in pre- and post-hurricane conditions. As habitat availability changed across years and islands, pelicans shifted from nesting in woody vegetation, to grasses, forbs, and bare ground. More chicks that survived until the age of 3 to 4.5 weeks old were from higher nests, and the loss of woody vegetation might have elicited colony abandonment. Habitat reduction was attributed to hurricane-induced erosion, and shoreline retreat was an average 5.5 times (range 3.3 to 11) greater than regional rates from 1887 to 2002. Furthermore, land loss (16% to 99% of vegetated regions) was restricted to areas without protective breakwaters. In addition to the effects of habitat decline on pelican reproduction, contamination by the Deepwater Horizon oil spill might have further decreased nest success. Large and productive seabird colonies can be rapidly degraded by both human and natural disturbance, making amelioration of such threats a management priority.

Within the context of a limited number of Brown Pelican (Pelecanus occidentalis) breeding sites, promoting new colonies can mitigate localized threats to regional populations. To assess the efficacy of short-distance (~5 km) translocations and use of decoys to establish new colonies, and thereby increase statewide population viability, research was conducted within the Isles Dernieres archipelago, Louisiana. Translocations of 323 Brown Pelican chicks to an un-colonized island were performed from 2007 to 2009, and from 2008 to 2010, 108 Brown Pelican decoys were deployed on a separate island void of nesting. From 2008 to 2010 band re-sighting surveys detected only one transplanted Brown Pelican chick that returned to the release site. Further, < 1% of translocated individuals were observed throughout the archipelago, compared to 5% and 9% of banded individuals encountered that fledged from nearby islands. Low detection of translocated Brown Pelicans may be due to translocation stress that can result in disorientation and social disorganization, which may promote increased roaming. At sites with decoys, no loafing or nesting Brown Pelicans were observed. Further, behavioral surveys suggest there was no difference in interest of passing Brown Pelicans to decoys compared to paired control survey areas without decoys. Despite past successes of translocations and decoys for establishing new colonies of Brown Pelicans and other waterbird species, Brown Pelican conservation may be best promoted via restoration and protection of current colony sites. Received 6 April 2012, accepted 17 October 2012.

Regenerating forests are increasingly ubiquitous in tropical landscapes. They hold great conservation potential and there is demand for assessments of their biodiversity value. Forest disturbance and forest loss often occur together, yet few studies attempt to disentangle their separate effects on biological communities. In the Ecuadorian Chocó, a biodiversity hotspot, we sampled understory birds in patches with increasing levels of disturbance (old-growth, selectively-logged, and secondary forests) within contiguous forest and in fragments. Species richness increased with disturbance but decreased with habitat loss, with a 75% reduction in endemic and threatened species in fragments compared to contiguous forest. This reduction in richness was most pronounced in secondary forest fragments, suggesting that disturbance and habitat loss interact synergistically to maximally reduce avian biodiversity. Species composition was strongly affected by habitat loss and, to a lesser extent, disturbance, with forest fragments and secondary forests presenting distinct communities dominated by generalists with medium-to-low sensitivity to anthropogenic disturbance and reduced proportions of endemics and endangered species. Capture rates also decreased (non-significantly) with habitat loss, and the relative abundance of dietary guilds varied in response to both habitat loss and disturbance. Our study shows that regenerating patches surrounded by contiguous forest can sustain high biodiversity levels and, when past habitat disturbance is mild, present similar communities to old-growth forests. In contrast, forest loss caused reductions in richness (especially in more disturbed patches), profound changes in community composition, and loss of species of conservation concern. These results underscore the importance of considering landscape context when evaluating the conservation value of disturbed forests

Phylogeny, ecological environment, social organisation, and mating system are expected to affect degree of female ornamentation, either directly or indirectly, but our understanding of how female ornaments respond to these forces remains incomplete. This article evaluates the evolutionary history and adaptive significance of three putative ornaments – plumage colouration, bill colouration and tail-length – in female fairy-wrens. Despite considerable research on these traits in male fairy-wrens, they have yet to be studied in any detail in females. Phylogeographic analyses in combination with lifehistory data suggest that female plumage colouration and bill colouration are under active selection, independent of that experienced by males. Social organisation and mating system, as mediated by ecological environment, may shape degree of ornamentation in these traits among females. In contrast, tail-length appears to be driven directly by natural ecological selection imposed by environmental conditions, leading to parallel trait evolution among the sexes within each species. More refined comparative and population-level investigations of adaptive consequences and proximate mechanisms are future research priorities. The study of female fairy-wrens holds great promise to advance our collective understanding of how the ecological environment interacts with sexual selection and social competition to shape ornament evolution in complex social organisms.

BACKGROUND: Many species exhibit geographic variation in sexual signals, and divergence in these traits may lead to speciation. Sexual signals may diverge due to differences in ecology if the environment constrains signal production or transmission. Alternatively, sexual signals may diverge stochastically through sexual selection or genetic drift, with little environmental influence. To distinguish between these alternatives we quantified variation in two putative sexual signals–tail length and plumage color–and a suite of non-sexual morphometric traits across the geographic range of the red-backed fairy-wren (Malurus melanocephalus). We then tested for associations between these traits and a number of environmental variables using generalized dissimilarity models.

RESULTS: Variation in morphometric traits was explained well by environmental variation, irrespective of geographic distance between sites. Among putative signals, variation in plumage color was best explained by geographic distance, whereas tail length was best explained by environmental variation. Divergence in male plumage color was not coincident with the boundary between genetic lineages, but was greatest across a contact zone located 300 km east of the genetic boundary.

CONCLUSIONS: Morphometric traits describing size and shape have likely been subject to ecological selection and thus appear to track local environmental variation regardless of subspecies identity. Ecological selection appears to have also influenced the evolution of tail length as a signal, but has played a limited role in shaping geographic variation in plumage color, consistent with stochastic divergence in concert with Fisherian selection on this trait. The lack of coincidence between the genetic boundary and the contact zone between plumage types suggests that the sexual plumage signal of one subspecies has introgressed into the genetic background of the other. Thus, this study provides insight into the various ways in which signal evolution may occur within a species, and the geographic patterns of signal variation that can arise, especially following secondary contact.

Many species of flamingo are endangered in the wild but common in zoos, where successful captive breeding programs are a management priority. Unlike their counterparts in the wild, captive flamingo individuals are easy to mark and follow, facilitating longitudinal data collection on social dynamics that may affect reproduction. We studied a captive group of American Flamingos at the Audubon Zoo in New Orleans, LA to document patterns of aggression between individuals during the onset of breeding. We used a social network approach to test whether overall aggression would be higher during courtship or following establishment of pair bonds. Aggression was higher following pair bond establishment than during courtship, suggesting that individuals in our study population may compete more intensely for resources such as nesting sites than for mates. We also found that males were more aggressive than females during all stages of the study period and that there was a positive relationship between age and aggression in males during the pair-bond stage. We discuss these findings in light of management practices for captive populations of flamingos and general patterns of aggression in social animals.