The anatomy of the bill tip of kiwi and associated somatosensory regions of the brain : comparisons with shorebirds

Three families of probe-foraging birds, Scolopacidae (sandpipers and snipes), Apterygidae (kiwi), and Threskiornithidae (ibises, including spoonbills) have independently evolved long, narrow bills containing clusters of vibration-sensitive mechanoreceptors (Herbst corpuscles) within pits in the bill-tip. These ‘bill-tip organs’ allow birds to detect buried or submerged prey via substrate-borne vibrations and/or interstitial pressure gradients. Shorebirds, kiwi and ibises are only distantly related, with the phylogenetic divide between kiwi and the other two taxa being particularly deep. We compared the bill-tip structure and associated somatosensory regions in the brains of kiwi and shorebirds to understand the degree of convergence of these systems between the two taxa. For comparison, we also included data from other taxa including waterfowl (Anatidae) and parrots (Psittaculidae and Cacatuidae), non-apterygid ratites, and other probe-foraging and non probe-foraging birds including non-scolopacid shorebirds (Charadriidae, Haematopodidae, Recurvirostridae and Sternidae). We show that the bill-tip organ structure was broadly similar between the Apterygidae and Scolopacidae, however some inter-specific variation was found in the number, shape and orientation of sensory pits between the two groups. Kiwi, scolopacid shorebirds, waterfowl and parrots all shared hypertrophy or near-hypertrophy of the principal sensory trigeminal nucleus. Hypertrophy of the nucleus basorostralis, however, occurred only in waterfowl, kiwi, three of the scolopacid species examined and a species of oystercatcher (Charadriiformes: Haematopodidae). Hypertrophy of the principal sensory trigeminal nucleus in kiwi, Scolopacidae, and other tactile specialists appears to have co-evolved alongside bill-tip specializations, whereas hypertrophy of nucleus basorostralis may be influenced to a greater extent by other sensory inputs. We suggest that similarities between kiwi and scolopacid bill-tip organs and associated somatosensory brain regions are likely a result of similar ecological selective pressures, with inter-specific variations reflecting finer-scale niche differentiation.

Upland Nesting Prairie Shorebirds: Use of Managed Wetland Basins and Accuracy of Breeding Surveys

Wetlands in southern Alberta are often managed to benefit waterfowl and cattle production. Effects on other species usually are not examined. I determined the effect of managed wetlands on upland-nesting shorebirds in southern Alberta by comparing numbers of breeding willets (Catoptrophorus semipalmatus), marbled godwits (Limosa fedoa), and long-billed curlews (Numenius americanus) among areas of managed wetlands, natural wetland basins, and no wetland basins from 1995 to 2000. Surveys were carried out at 21 sites three times each year. Nine to ten of these areas (each 2 km2) were searched for nests annually from 1998–2000. Numbers of willets and marbled godwits and their nests were always highest in areas with managed wetlands, probably because almost all natural wetland basins were dry in this region in most years. Densities of willets seen during pre-incubation surveys averaged 2.3 birds/km2 in areas of managed wetlands, 0.4 in areas of natural wetland basins, and 0.1 in areas with no wetland basins. Nest densities of willets (one search each season) averaged 1.5, 0.9, and 0.3 nests/km2 in areas of managed, natural, and no wetland basins, respectively. Similarly, pre-incubation surveys averaged 1.6, 0.6, and 0.2 godwits/km2 in areas of managed, natural, and no wetland basins, and 1.2, 0.3, and 0.1 godwit nests/km2. For long-billed curlews, pre-incubation surveys averaged 0.1, 0.2, and 0.1 birds/km2, and 0, 0.2, and 0 nests/km2. Nest success was similar in areas with and without managed wetlands. Shallow managed wetlands in this region appear beneficial to willets and marbled godwits, but not necessarily to long-billed curlews. Only 8% of marked willets and godwits with nests in the area were seen or heard during surveys, compared with 29% of pre-laying individuals and 42% of birds with broods. This suggests that a low and variable percentage of these birds is counted during breeding bird surveys, likely limiting their ability to adequately monitor populations of these species.

Can oiled shorebirds and their nests and eggs be successfully rehabilitated? A case study involving the threatened Hooded plover Thinornis rubricollis in South-eastern Australia

Although shorebirds are detrimentally affected by marine oil spills, they are often overlooked during rescue and rehabilitation efforts. This note describes a rescue and successful rehabilitation effort of an oiled adult and a juvenile Hooded Plover (Thinornis rubricollis) in Victoria, south-eastern Australia, during an oil-spill which oiled almost 1% of the State’s population of this threatened beach-nesting species. Two birds requiring intervention were located, selectively captured, cleaned and released. Both have survived at least two years after the spill and have bred, with at least one successfully fledging young. The fledgling has also successfully bred. Two nests with eggs present during clean-up operations were protected and hatched successfully. This small case study indicates that at least some groups of breeding shorebirds, such as plovers and dotterels, can be effectively rescued and rehabilitated during oil spills, and hence should not be overlooked during such circumstances.

Combining the forces of science and conservation to turn around the fortunes of shorebirds

At the start of the 21st century the majority of migratory wader (shorebird) populations are faced with serious threats. This commonly results from the continuous destruction of wetlands, their key habitat. Healthy wetlands are highly biodiverse and extremely vulnerable, and as functioning ecosystems particularly important for us humans for a sustained livelihood (artisanal fisheries, small-scale farming) and our well-being (effective water filtering and cleaning systems). In many parts of the world, wetlands have been seen as wastelands, or even as a source of threat (malaria). Many freshwater wetlands have been drained for agricultural use and mudflats have been reclaimed for settlement and urbanization. Wetlands are continuously squeezed by economic development and increasingly used for recreational activities, and their resources are, in general, notoriously overexploited.

Brains and bravery: little evidence of a relationship between brain size and flightiness in shorebirds

The ability of birds to perceive, assess and appropriately respond to the presence of relatively novel threats is important to their survival. We hypothesized that the cognitive capacity of birds will influence their ability for accurate response to novelty. We used brain volume as a surrogate for cognitive capacity and postulated that larger brained birds would moderate their responses when presented with a benign, frequently occurring stimulus, such as a person, because they would habituate more readily. We conducted phylogenetic generalized least square regression to investigate the relationship between brain volume and flight initiation distance (FID; the distance to which a bird can be approached before initiating escape behaviour), while controlling for confounding factors including body size (body mass and wing length) and migration status. We compared seven different models using combinations of these parameters using Akaike's information criterion to determine the best approximating model(s) explaining FID. The two best-supported models included only wing length and only body mass with Akaike weights of 0.396 and 0.311 respectively. No model including brain volume had an Akaike weight greater than 0.083 and brain volume was poorly correlated with FID in models after controlling for body mass. Thus, brain volume does not appear to strongly relate to bravery among these shorebirds.

Do temporary beach closures assist in the conservation of breeding shorebirds on recreational beaches?

Recreational use of beaches may threaten some beach-nesting shorebirds in southern Australia. Temporary Beach Closures, comprized of a 50 x 25 m exclusion zone around a shorebird nest, represent a promising technique for altering human behaviour by reducing both disturbance to birds and inadvertent crushing of eggs by beach visitors. We assessed whether three commonly employed configurations of Temporary Beach Closures (sign, fence, and warden) were effective at: (1) achieving compliance among beach visitors, and (2) reducing egg-crushing rates. Overall, 93.7% of beach visitors complied with all Temporary Beach Closures, resulting in a reduction in egg-crushing rates within, as opposed to adjacent to, Temporary Beach Closures. Levels of compliance were high in all Temporary Beach Closure configurations (88.0-99.4%), and similar levels of compliance were achieved within the three configurations. Human compliance was highest for females and when the density of beach-users was higher, while individuals aged <20 and >61 years were less likely to comply with Temporary Beach Closures. Despite an increased probability of compliance on high density beaches, this did not translate into a reduction in egg crushing rates on such beaches, because the overall number of noncompliant individuals remained higher. We conclude any Temporary Beach Closure configuration is meritorious, and that their use on high and low-use recreational beaches will benefit breeding shorebirds by reducing the rate of egg-crushing. Targeting demographics that display lower levels of compliance, such as men, young people (i.e. <21), and older people (i.e. >60), may further improve the effectiveness of Temporary Beach Closures in enhancing the conservation of shorebirds.

Molecular sex-typing in shorebirds: a review of an essential method for research in evolution, ecology and conservation

Knowing the correct sex of individuals is essential both for research in evolutionary ecology and for practical conservation. Recent molecular advances have produced cheap, quick and reliable methods for sexing birds including chicks, juveniles, immatures and adults. Shorebird researchers have not yet fully utilised these advances. Here we provide an overview of work in this area to date with two objectives: (i) to review the major applications of molecular sexing and findings of shorebird research so far, and (ii) to provide an essential guide on how to carry out molecular sexing using current methods whilst avoiding methodological pitfalls. We encourage shorebird researchers to make better use of molecular sex-typing techniques in studies of conservation, migration, foraging ecology and breeding behaviour.

High basal metabolic rates of shorebirds while in the Arctic: a circumpolar view

The basal metabolic rate (BMR) of Old World long-distance-migrant shorebirds has been found to vary along their migration route. On average, BMR is highest in the Arctic at the start of fall migration, intermediate at temperate latitudes, and lowest on the tropical wintering grounds. As a test of the generality of this pattern, we measured the BMR of one adult and 44 juvenile shorebirds of 10 species (1-18 individuals of each species, body-mass range 19-94 g) during the first part of their southward migration in the Canadian Arctic (68-76°N). The interspecific relationship between BMR and body mass was almost identical to that found for juvenile shorebirds in the Eurasian Arctic (5 species), although only one species appeared in both data sets. We conclude that high BMR of shorebirds in the Arctic is a circumpolar phenomenon. The most likely explanation is that the high BMR reflects physiological adaptations to low ambient temperatures. Whether the BMR of New World shorebirds drops during southward migration remains to be investigated.

Coexistence between Nearctic-Neotropical migratory shorebirds and humans on urban beaches of the Southern Hemisphere: a current conservation challenge in developing countries

The arrival of migratory shorebirds on beaches in urban communities in developing countries is a current challenge for the protection of these migrant birds. Nearctic-Neotropical migrants rely on roosting and feeding sites during their stopover on wintering sites in the Southern Hemisphere to acquire sufficient energy to complete their migratory cycles. On the other hand, cities in the Southern Hemisphere are growing rapidly, which results in increasing competition for space between humans and birds, such as for use in beach habitats. In the present study, I analyze the probability for occurrence for Nearctic-Neotropical migratory birds relative to the number of people in southeastern Brazil, the most populated region of South America. The frequency of occurrence of migrants, their distance of tolerance to people and the number of people were recorded in sample areas (circle plots with 20 m radius) on a 9 km stretch of urban beaches from November to February from 2009 to 2013. The probability of occurrence of Nearctic birds decreased as the number of people increased. When the number of people exceeded 20, the probability of occurrence of birds was almost zero. Furthermore, more than 95 % of birds moved off when people were within 16 m of reach. These results are discussed in the context of conservation actions since no management plan has been developed for migrant shorebirds that use urban beaches as stopover or wintering sites in developing countries.

Investigating Avian Influenza Infection Hotspots in Old-World Shorebirds

Heterogeneity in the transmission rates of pathogens across hosts or environments may produce disease hotspots, which are defined as specific sites, times or species associations in which the infection rate is consistently elevated. Hotspots for avian influenza virus (AIV) in wild birds are largely unstudied and poorly understood. A striking feature is the existence of a unique but consistent AIV hotspot in shorebirds (Charadriiformes) associated with a single species at a specific location and time (ruddy turnstone Arenaria interpres at Delaware Bay, USA, in May). This unique case, though a valuable reference, limits our capacity to explore and understand the general properties of AIV hotspots in shorebirds. Unfortunately, relatively few shorebirds have been sampled outside Delaware Bay and they belong to only a few shorebird families; there also has been a lack of consistent oropharyngeal sampling as a complement to cloacal sampling. In this study we looked for AIV hotspots associated with other shorebird species and/or with some of the larger congregation sites of shorebirds in the old world. We assembled and analysed a regionally extensive dataset of AIV prevalence from 69 shorebird species sampled in 25 countries across Africa and Western Eurasia. Despite this diverse and extensive coverage we did not detect any new shorebird AIV hotspots. Neither large shorebird congregation sites nor the ruddy turnstone were consistently associated with AIV hotspots. We did, however, find a low but widespread circulation of AIV in shorebirds that contrast with the absence of AIV previously reported in shorebirds in Europe. A very high AIV antibody prevalence coupled to a low infection rate was found in both first-year and adult birds of two migratory sandpiper species, suggesting the potential existence of an AIV hotspot along their migratory flyway that is yet to be discovered.