Demography of Bristle-thighed Curlews Numenius tahitiensis wintering on Laysan Island

We studied the nonbreeding ecology of Bristle-thighed Curlews Numenius tahitiensis from 1988 to 1991 on Laysan Island in the Northwestern Hawaiian Islands. Using capture-recapture analysis, we estimated that 300–350 curlews wintered on the island. Annual survival was >85% for adults and 92% for first-year birds. Young birds remained on the island until at least their third calendar year, when some individuals made "exploratory" visits to other islands in the Northwestern chain. Most of the birds marked in their first year migrated north to the breeding grounds when they were 3 years old; several birds remained on the island until they were at least 4 years old. Adults returned to the same discrete home ranges year after year, whereas subadults (which do not migrate) tended to use a greater portion of the island. At least 60% of the subadults marked from 1988 to 1990 returned to the island to winter as adults. Because young curlews arrived after adults and experienced high survivorship while on the island, there did not appear to be intense competition for space at Laysan even though the island is at the northern end of the species' winter range.     

温州地区小杓鹬的代谢产热特征

动物能量代谢相关的生理生态特征与其地理分布密切相关。为探讨温州地区迁徙鸟类小杓鹬(Numenius minutus)的代谢产热特征及体温调节,本文在环境温度(T_a)5.0～42.5℃范围内,测定了小杓鹬的代谢率(R_m,以单位时间耗氧量表示,ml/h)和体温,并计算不同环境温度的热传导。结果显示：在环境温度为5～35℃的范围内,小杓鹬的体温维持相对恒定,平均体温为(42.8±0.10)℃;热中性区为27.5～40.0℃;在热中性区温度范围内,代谢率即基础代谢率为(221.31±6.01)ml/h,是体重预期值的141%;环境温度在5.0～27.5℃范围内,代谢率与环境温度(T_a,℃)呈负相关,回归方程为R_m=587.10﹣11.78 T_a;在5.0～27.5℃的环境温度范围内,小杓鹬的热传导最低,平均为(0.11±0.00)ml/(g·h·℃),是体重预期值的212%;代谢预期比和热传导预期比的比值(F值)为1.21,表明该物种有较好的体温调节能力。小杓鹬具有较高的体温和基础代谢...     

Sex roles, parental effort and offspring desertion in the monogamous Eurasian Curlew Numenius arquata

The reasons for female desertion of offspring and the evolution of predominantly male care among monogamous bird species are not clearly understood. We studied parental effort during the incubation and chick rearing periods in the Eurasian Curlew Numenius arquata in western Finland, and compared timing of brood desertion with other populations in Europe. Males and females contributed equally to incubation and showed no differences in the intensity of mobbing behaviour towards a potential nest predator (stuffed crow) shortly after hatching. However, females deserted their offspring approximately halfway through the brooding period ( c. 16 d after hatching), while males remained with chicks until independence ( c. 35 d). Females with late-laid clutches deserted their offspring sooner after hatching than those with clutches produced earlier in the season. Curlew females deserted younger chicks in northeast Europe, where laying dates were later, breeding seasons shorter and migration distances were longer, than in western and central Europe. We suggest that the most likely reasons for offspring desertion by females may be associated with increased female survivorship and maintenance of pairbond between years.     

Effects of radiotagging on the weight gain and survival of Curlew Numenius arquata chicks

CapsuleNo detrimental effects on weight gain or survival to fledging stage were found.

Aims To assess the effects of radiotagging on the weight gain and survival of Curlew chicks.

Methods Small (≤ 1.5 g) radiotags were attached to Curlew chicks at hatching, during studies in four different areas of the UK. Tagged chicks were recaptured regularly and their weight gain and survival compared to non-tagged chicks using within and between-brood comparisons.

Results Radiotagging did not affect weight gain. While there was no evidence of reduced survival of tagged chicks, comparisons were based on small samples.

Conclusions Small radiotags can be invaluable in determining the survival and causes of mortality of the chicks of waders and other precocial birds.     

Estimating the abundance and hatching success of breeding Curlew Numenius arquata using survey data

Counts of individual Curlew and estimates of breeding pairs from ‘field-by-field’ surveys were highly correlated with the numbers of nesting pairs, as determined by intensive studies on 27 sites located on four grassland-dominated study areas. The mean count of individual Curlew over three standard survey visits to each site was used to estimate numbers of nesting pairs. This estimate exceeded the number of nesting pairs on all study areas (as assessed by intensive studies) by 12% but was more accurate than the maximum number of pairs estimated from the three survey visits on each site (the previous convention for estimating breeding pairs). Estimates of the number of pairs hatching chicks were assessed by recording alarm-calling Curlew during late survey visits. The maximum number of alarm-calling pairs was used to estimate the number of pairs hatching chicks, overestimating this by 54%. Three of the study sites were adjacent to extensive moorland which produced overestimates during surveys because moorland nesting birds fed and led broods onto these sites. Omitting these sites from consideration reduced the degree of overestimation to 1% for the number of pairs and 7% for the number of pairs hatching chicks.     

Correlates of distribution and nesting success in a Welsh upland Eurasian Curlew Numenius arquata population

Capsule: Habitat structure and composition explained spatial variation in breeding distribution and nesting success in a declining upland Eurasian Curlew Numenius arquata population in North Wales.

Aims: To identify environmental correlates of Curlew breeding distribution, nesting success and change in distribution.

Methods: Thirty random 1?km squares stratified by historical population trend were surveyed for Curlew density and nesting success, and habitat- and predation-related variables in a landscape containing agriculturally improved farmland, and moorland that was partly protected and subject to grazing reductions for nature conservation. Analyses tested for associations between Curlew measures and environmental variables.

Results: Curlew breeding density declined by 29% between 1994 and 2008, and was highest in squares comprising a mixture of moorland and agriculturally improved farmland, and in squares with lower vegetation density and higher cover of Nardus stricta (characteristic of rough grazing). Nesting success was positively associated with cover of Trichophorum germanicum (characteristic of mire). Vegetation density was lower than average in squares with the highest Curlew densities, while in the protected area vegetation density was higher than average.

Conclusion: Habitat and vegetation variables influenced Curlew distribution and nesting success in North Wales, largely in line with previous results but with no evidence for predator-related influences. Habitat condition for Curlew in the protected area could probably be increased through targeted increases in grazing alongside the protection of priority habitats.     

Population density and the intensity of paternity assurance behaviour in a monogamous wader: the Curlew Numenius arquata

We compared paternity assurance behaviour and related displays in high (1.6 pairs perkm²) and low (6.7 pairs per km²) density populations of the Curlew Numenius arquata breeding on arable farmland in western Finland. There was little evidence of individuals pursuing extra-pair copulations or males exhibiting paternity assurance behaviour. Furthermore, there was no variation in the frequency of intrusions or in the intensity of paternity assurance behaviour relative to lay date. However, intrusions and approaches to the pair female by extra-pair males were more frequent at high breeding density, and pair males remained closer to their female, followed her more and exhibited a higher frequency of copulatory behaviours in the high-density population. Therefore, high breeding density appeared to increase opportunities for individuals to copulate outside the pair-bond and resulted in more intense male paternity guards. Male song flight displays were also more frequent in the high-density population. Territorial absences by males were infrequent in both areas. The increased frequency of intrusions and interactions between non-pair individuals (male-male and male-female) at high density were probably the major factors in explaining area differences in the intensity of paternity assurance and territorial behaviour.     

Environmental correlates of breeding abundance and population change of Eurasian Curlew Numenius arquata in Britain

Capsule: Across Britain, breeding Eurasian Curlew Numenius arquata are less numerous and have shown greater population declines in areas with more arable farming, woodland cover and higher generalist predator abundance.

Aims: We present the first national-scale analysis of the potential drivers of Curlew population change in Britain, which is needed to guide conservation action for this globally near-threatened, declining species.

Methods: Breeding Bird Survey data and environmental predictors were used to model variation in Curlew abundance in 1995–99 and 2007–11, and population change between these periods.

Results: Arable farming and woodland cover were negatively associated with Curlew abundance and population declines. Curlew abundance was positively associated with extent of protected area coverage and gamebird numbers. Abundance and population change were positively associated with cooler temperatures and higher summer rainfall, but negatively associated with numbers of generalist predators.

Conclusions: We found support for the negative effects of intensive agriculture, forestry, increases in generalist predator populations and climate warming on Curlew abundance and population change. Effective site protection and measures to reduce generalist predator abundance may be important conservation measures, together with improving breeding habitat quality in the wider countryside.     

Values and perceptions of landowners within remaining breeding territories of Eurasian Curlew Numenius arquata in Ireland

Habitat loss and degradation have been identified as some of the main threats to breeding Curlew (Numenius arquata) across much of Europe. In Ireland, marginal habitats such as rough or wet grasslands and peatlands have been fragmented or degraded by activities including afforestation, drainage and intensification. The management implemented by landowners directly affects Curlew breeding territories. However, the values and perceptions held by landowners whose lands contain Curlew breeding territories, or the factors driving the decisions behind farming practices in these areas are rarely considered when looking at the causes of changes in these bird populations. This study, as part of the Curlew Conservation Programme established in 2017, gathered data through the distribution of questionnaires to landowners found within three kilometres of Curlew breeding territories in Ireland. In this study, we identify the current land uses being employed in Curlew breeding territories, and query future projections of land use in these areas. We investigate landowners’ perceptions of the requirements to sustain favourable environments for breeding Curlew. We also explore landowner values with respect to farming. The landowners in this study identified habitat loss and predation as the main drivers for Curlew declines. The majority of farming systems in this study were cattle rearing, the sustainability of which is under threat across Ireland. The results indicate that these landowners are not financially motivated, however, the availability of financial aid and expert advice are listed by landowners as requirements for traditional farming practices to continue. These results give an insight to the lifestyle, values and perceptions owners of land adjacent or within Curlew breeding territories. This information can be used to design Curlew conservation programmes that align with these values.     

Placement,survival and predator identity of Eurasian Curlew Numenius arquata nests on lowland grass-heath

ABSTRACT

Capsule

Within the UK’s largest lowland Eurasian Curlew Numenius arquata population, curlew preferentially nested on physically disturbed (treated) than undisturbed (control) grassland, and low nest survival rates were primarily attributable to predation by Red Fox Vulpes vulpes.     

Population estimates,trends and habitat associations of breeding Lapwing Vanellus vanellus,Curlew Numenius arquata and Snipe Gallinago gallinago in Northern Ireland in 1999

Capsule Declines in the breeding populations of Snipe, Lapwing and Curlew were recorded between April and June 1999 and compared with previous estimates in 1987.

Aims To compare populations of non-coastal breeding waders between 1987 and 1999.

Methods In 106 2 km × 2 km square tetrads, observers recorded the number of breeding pairs of waders and habitat details on 1:10 000 scale maps.

Results A significant decline of c. 60% for Lapwing and Curlew, and a non-significant decline of 30% for Snipe was recorded over 12 years. Concentrations of these species were found in County Tyrone, but Counties Antrim, Down and Armagh supported few breeding pairs of any species. Very few pairs of any species were recorded on improved grassland despite its widespread availability.

Conclusion A successful conservation strategy for these species must address the wider countryside and not just key sites. Intensive pastoral farming in upland and lowland areas and activities such as drainage and peat extraction will further reduce the suitability of open habitats for these wader species.     

High fidelity to wintering,stop-over and breeding sites shown by a Long-billed Curlew Numenius americanus tracked with satellite telemetry on migratory flights across North America

Capsule We studied the migratory movements and site fidelity of a male Long-billed Curlew using satellite telemetry in North America; the bird completed three migratory cycles and showed strong fidelity to stop-over, breeding, and wintering sites, not only on a geographical scale but also on a local scale across the years.     

Regenerative and reproductive capacities of the fissiparous planarian Dugesia tahitiensis

A pilot study was performed to assess the regenerative capacities of Dugesia tahitiensis Gourbault, 1977, an exclusively fissiparous planarian species. Animals measuring 9.5–12.5 mm in length were used. Head regeneration rate determined by the appearance of eye spots (Brødsted, 1969: 29–46) was extremely high: at 23 °C, it took 43–59 h to regenerate clearly discernible eye spots in 28 specimens. For comparison, 3.8 days were reported for the regeneration of eye spots in 11.9–12.7 mm long D. tigrina (Girard) at 24 °C (Mead, 1985). As all posterior fragments regenerated a head, irrespective of the cutting level, D. tahitiensis seems to match the Phagocata velata (Stinger) type with a head frequency of 100% at every level (Teshirogi et al., 1977; cf. also Brøndsted, 1969:30).     

Estimating the Breeding Population of Long-Billed Curlew in the United States

ABSTRACT Determining population size and long-term trends in population size for species of high concern is a priority of international, national, and regional conservation plans. Long-billed curlews (Numenius americanus) are a species of special concern in North America due to apparent declines in their population. Because long-billed curlews are not adequately monitored by existing programs, we undertook a 2-year study with the goals of 1) determining present long-billed curlew distribution and breeding population size in the United States and 2) providing recommendations for a long-term long-billed curlew monitoring protocol. We selected a stratified random sample of survey routes in 16 western states for sampling in 2004 and 2005, and we analyzed count data from these routes to estimate detection probabilities and abundance. In addition, we evaluated habitat along roadsides to determine how well roadsides represented habitat throughout the sampling units. We estimated there were 164,515 (SE=42,047) breeding long-billed curlews in 2004, and 109,533 (SE=31,060) breeding individuals in 2005. These estimates far exceed currently accepted estimates based on expert opinion. We found that habitat along roadsides was representative of long-billed curlew habitat in general. We make recommendations for improving sampling methodology, and we present power curves to provide guidance on minimum sample sizes required to detect trends in abundance.     

Brood desertion in Kentish plover: the value of parental care

To understand the evolution of parental care, one needs to estimatethe payoffs from providing care for the offspring and from terminatingcare and deserting them. In this study we estimated the payofffrom care provision, and in a companion paper we analyze thepayoff from offspring desertion. In the current study we experimentallyinvestigated the influence of the number and sex of attendingparents on growth and survival of offspring in the Kentish ploverCharadrius alexandrinus, in two sites (A and B). Either the maleor the female parent was removed from some broods at hatchingof the chicks (female-only and male-only broods, respectively),whereas in control broods both parents were allowed to attendtheir young. At site A survival of the chicks was lower in uniparental(male-only and female-only) broods than in control broods, whereaswe found no difference in brood survival at site B. Brood survivaldecreased over the season. Removal of either parent did not influencethe growth of the young, although growth varied over the breeding season,and it was significantly different between the sites. Theseresults suggest that the payoff from parental care decreasesover the breeding season and that the value of parental care(i.e., the contribution of parents to the survival of theiryoung) may depend on the environment.     

Brood sex ratio in the Kentish plover

How and why do the mating opportunities of males and femalesdiffer in natural population of animals? Previously we showedthat females have higher mating opportunities than males inthe Kentish plover Charadrius alexandrinus. Both parents incubatethe eggs, and males provide more brood care than females; thusit is not obvious why the females find new mates sooner thanthe males. In this study we investigated whether the sex-biasedmating opportunities stem from biased offspring sex ratios.We determined the sex of newly hatched, precocial chicks usingCHD gene markers. Among fully sexed broods, 0.461 ± 0.024(SE) of chicks (454 chicks in 158 broods) were male, and thissex ratio was not significantly different from unity. The proportionof males at hatching decreased significantly over the breedingseason, which occurred consistently in all 3 years of the study.Large chicks were more likely to be males than females. Neitherparental age nor body size of male and female parents was relatedto brood sex ratio. We also sexed a number of chicks that werecaught after they left their nest (range of estimated ages 0–17days) and found that the proportion of males increased withbrood age. This relationship remained highly significant whencontrolling statistically for hatching date. As brood size decreaseddue to mortality after the chicks left their nest, these resultssuggest that the mortality of daughters was higher than thatof the sons shortly after hatching. Taken together, our resultsshow that the female-biased mating opportunities in the Kentishplover are not due to biased brood sex ratio at hatching but,at least in part, are due to female-biased chick mortality soonafter hatching.     

On the migration of the Whimbrel,Numenius phaeopus,in Turkey

Abstract

The Whimbrel (Numenius phaeopus) is a scarce but regular passage visitor in Turkey. Spring migration has its peak in April, autumn migration in August/September (medians are April 23th and August 29th). Detailed information on flock size, wintering, main resting sites etc. is given and compared with other Middle East countries.     

Brood reduction in temperate and sub-tropical ospreys

Summary In an effort to understand patterns and causes of nestling loss in Ospreys (Pandion haliaetus), I studied brood reduction in three eastern U.S. Osprey colonies during 1978 and 1979. The colonies, located in Florida Bay (1) and on coastal Long Island, N.Y. (2), differed in the average daily amount of food delivered to nestlings; Florida nests received 43% and 11% less fish per day than nests in the two N.Y. colonies, largely because latitude and season restricted day length and thus foraging time for the winter-breeding Florida Ospreys. Increased distance from stable food sources accounted for the lower rate of feeding at one of the N.Y. colonies. Variation in clutch size in the three colonies reflected differences in latitude more than in food availability; average clutch sizes in Long Island were larger than Florida clutches by 0.5 of an egg, but were similar to each other and to those in other northeastern U.S. Osprey populations.Increased nestling loss coincided with reduced food delivery rates and, in food stressed colonies, this loss was 2–3 times greater than any recorded for Ospreys. Starvation was the primary cause of nestling death, with mortality concentrated on third chicks, which hatched on average 3.9 d later and from eggs 5.6% smaller than chicks hatching first. Sibling aggression accounted for the preferential feeding of older nestmates,but only in colonies or nests where food was limited. Aggressive chicks nearly always stopped fighting after being fed. This behavior provided a reversible mechanism for controling brood reduction that was based on nutrition. Growth rates of young measured during the first half of the growth period were more variable between colonies than within nests. This is interpreted as reflecting both the differences in colony food delivery rates as well as the evolutionary pressures of sibling competition to equalize the growth of nestmates.     

Brood reduction in the Blue-eyed Shag Phalacrocorax atriceps

Brood reduction is common in a population of Blue-eyed Shags on Signy Island, South Orkney Islands. This paper describes possible adaptations which may reduce the brood. In clutches of three, the last egg was smaller, and hatched 2.4 days later than its siblings. Whilst 78–84% of first and second ('A' & 'B') chicks fledged, only 11 % of 'C' chicks did. In a sample of artificially synchronized broods chick survival was as high as in normal asynchronously hatching broods, but there were more cases of total brood loss. The age at which the C chick died was related inversely to the length of the A-C hatching interval. Relative differences in sibling weights were highest during the first 12 days, when most of the C chick deaths occurred. At this age the daily food requirements of each brood of three was one-tenth that of each brood of two just prior to fledging. It is suggested that C chicks were unable to compete effectively for a food supply which was limited by the parents, rather than by the environment. The asymptotic weight attained by A chicks was inversely related to brood size, and was greater than that of B or C chicks. Normal asynchronous broods produced at least one heavy (A) chick and one medium weight (B) chick, whilst in synchronized broods the asymptotic weight attained was similar to that of B chicks in normal broods.