The effects of geolocators on return rates,condition, and breeding success in Common Sandpipers Actitis hypoleucos

ABSTRACT

Capsule: Fitting geolocators to Common Sandpipers Actitis hypoleucos did not affect their return rates, return dates, body condition or reproductive success, but did cause leg injuries in some individuals.

Aims: To investigate the effect of fitting geolocators to Common Sandpipers on their return rates and timing, the condition in which they return and their subsequent breeding success.

Methods: We fitted geolocators to colour-ringed Common Sandpipers and monitored them throughout the breeding seasons prior to migration and following return from their wintering grounds. We then compared return rate, return date, change in body condition, hatching success, and fledging success between birds with and without the tags. We also fitted a number of smaller geolocators to wintering individuals in Africa and compared their return rates with a control group.

Results: We found no significant differences between birds with and without geolocators in any of the variables measured. However, several individuals fitted with the larger tags were found to have incurred leg injuries.

Conclusion: Our study highlights the need for complete transparency when reporting the effects of geolocators and shows the importance of continuous monitoring of individuals when carrying out tracking studies.     

Comparative population dynamics of Common Sandpipers Actitis hypoleucos: living at the edge

Capsule Common Sandpiper populations at the edge of their range do not recruit so well.

Aims To compare the survival rates, breeding success and recruitment of a population near the edge of its range (Peak District) with one more centrally placed (Borders).

Methods Populations were censused weekly; adults and chicks were ringed, and apparent survival of adults determined by resighting colour-ringed birds. Breeding success was assessed from ringing chicks and the guarding behaviour of their parents over 3–4 weeks post-hatching.

Results Survival rates of adults and their breeding success were similar in the two sites. Recruits were rarely ringed chicks returning to near their natal site; they were usually newly recruited adults. In both, natal dispersal took returning chicks away from their natal site, by 3–6 km, but far more potential recruits returned to the Borders (51% compared with 4%). The population in the Borders was more variable, but recovered better from declines.

Conclusions There is no obvious difference in survival or reproductive rates that would explain the different recent fates of the two study populations. Differential survival over winter in West Africa (the presumed wintering grounds) is unlikely to explain the recent decline of the Peak District population, because conditions there should have affected the Borders population too. The Peak District population is exposed at the edge of the species' range, and it seems to be poorer breeding success across its general range that has caused the poorer recruitment there, and hence the decline.     

Population dynamics of Common Sandpipers Actitis hypoleucos in the Peak District of Derbyshire – a different decade

Capsule A report of the failure of a population to recover from a catastrophic snow storm.

Aims To examine why our study population of Common Sandpipers failed to recover from a sharp drop in 1989, caused by a severe late April snowstorm, when it had recovered from a similar event in 1981.

Methods Populations were censused weekly, with extra visits to ring adults and chicks. Hatching was assumed to have occurred if adults alarmed, and fledging if alarming continued for three weeks. Data from 1989–99 and 1979–88 were compared.

Results The recruitment of new adults to the population was much lower, but these recruits mostly came from other breeding areas, and the local recruits appeared to go elsewhere. Median dispersal distance is estimated as 3.3 km, sufficient to take most locally produced young adults outside the study area.

Conclusions We do not know if poorer breeding in the source populations for our birds, or poorer survival of first year birds over winter in West Africa, is the cause of the failure of this population to recover in the 1990s.     

Breeding density of Dippers Cinclus cinclus' Grey Wagtails Motacilla cinerea and Common Sandpipers Actitis hypoleucos in relation to the acidity of streams in south-west Scotland

The distribution of breeding pairs of Dippers Cinclus cinclus , Grey Wagtails Motacilla cinerea and Common Sandpipers Actitis hypoleucos was assessed along 18 streams in south-west Scotland during summer 1987, and the lengths of territories, occupied by 5 5 breeding pairs of Dippers, were measured. In each stream the water chemistry, physical structure (e.g. gradient, altitude, nature of bankside vegetation) and density of aquatic invertebrates was determined. The density of breeding pairs of dippers was significantly lower along streams of low pH (high acidity) and steep gradients, and territories were significantly longer at these sites compared with those of higher pH. Many of the invertebrate families that are important prey for Dippers were scarce at sites of low pH, particularly caddisfly larvae (Trichoptera) and mayfly nymphs (Ephemeroptera). The low numbers and large territories of breeding pairs of Dippers on acidic streams may be due to reduced density and diversity of macroinvertebrate prey. Stream pH was not an important correlate of the distribution or density of Grey Wagtails or Common Sandpipers. It is suggested that the lack of any similar effect of pH on these other two species compared with Dippers is attributable to differences in their feeding ecology.     

High reliability of linear censusing for Common Sandpiper (Actitis hypoleucos) breeding along upland streams in the Pyrenees,France

Capsule Three visits during the breeding season are sufficient to estimate breeding numbers of Common Sandpipers.     

Non‐breeding areas and timing of migration in relation to weather of Scottish‐breeding common sandpipers Actitis hypoleucos

The number of breeding common sandpipers has declined in Britain due to poorer return rates from non‐breeding areas. To investigate little known aspects of their annual cycle, breeding common sandpipers were fitted with geolocators to track their migrations and determine their non‐breeding areas. Ten tagged birds left Scotland on 9 July (median dates and durations are given throughout the abstract). Short‐term staging was carried out by some birds in England and Ireland, then for longer by most birds in Iberia before continuing to West Africa, arriving on 28 July. Six birds spent most of the non‐breeding season (October–February) on the coast of Guinea‐Bissau, suggesting that this is a key area. Single birds occurred in Sierra Leone, Guinea, the Canary Islands and western Sahara. The southward migration from Scotland took 17.5 d (range 1.5–24 d), excluding the initial fuelling period. The first northward movement from Africa was on 12 April. Staging occurred in either Morocco, Iberia or France. Arrival in Scotland was on 2 May. The northward migration took 16 d (range 13.5–20.5 d). The main migration strategy involved short‐ and medium‐range flights, using tail‐winds in most cases. Variation in strategy was associated with departure date; birds that left later staged for shorter durations. Coastal West Africa provides two major habitats for common sandpipers: mudflats associated with mangroves and rice fields. Although the area of mangrove has been depleted, the scale of loss has probably been insufficient to account for the decline in sandpiper numbers. Rice fields are expanding, providing feeding areas for water‐birds. Meteorological data during the migrations suggest that the weather during the southward migration is unlikely to contribute to a population decline but strong cross‐winds or head‐winds during the northward migration to the breeding grounds may do so.     

Fuel load,fuel deposition rate and stopover duration of the Common Sandpiper Actitis hypoleucos during the autumn migration

Capsule: Common sandpipers stopping over in a tidal marsh in northern Iberia during the autumn migration period showed a moderate mean fuel load and low fuel deposition rate, but relatively long stopover periods, suggesting a ‘hopping’ strategy of migration.

Aims: The main objectives of this paper were to analyse the stopover ecology of migrant Common Sandpipers at Txingudi coastal marshes, northern Iberia, in autumn.

Methods: Common sandpipers were captured during the autumn migration of 2007–2013 at the Txingudi marshlands (province of Gipuzkoa, northern Iberia). Data were obtained from a constant effort ringing station working on a daily basis.

Results: We observed a moderate fuel load and fuel deposition rate and long stopovers.

Conclusion: Our results suggest overall a ‘hopping’ migration strategy. When moving along the coast of northern Iberia, Common Sandpipers may not use key wetlands to gain much fuel, as found in other waders or in some wetlands of inland Iberia, but all coastal marshes seem to be potentially used in the same way.     

Sika deer distribution and habitat selection: the influence of the availability and distribution of food, cover, and threats

Large populations of sika deer occur in lowland heath, woodland, and grassland mosaics in southern England. Previous studies have focused on understanding single factors potentially affecting distribution and habitat selection of sika deer rather than considering simultaneously effects of landscape configuration and human disturbance on their distribution and habitat selection. This study measured effects of habitat availability, landscape structure, and human disturbance on where sika deer placed their home ranges and habitat selection within those ranges. Two main hypotheses were tested: (1) habitat selection differs according to landscape structure and habitat availability at both landscape and home range scales and (2) distribution of sources of human disturbance within the home range of deer affects their distribution. Results from radiotracking 31 females provided support for the first hypothesis and partial support for the second. Habitat selection at the landscape and home range scales differed between landscapes with different habitat structure and availability and was driven by distribution and availability of food and cover and a perceived risk linked to disturbance. Furthermore, deer selected open areas close to cover and this selection was stronger with presence of human disturbance, although results differed between study areas with different habitat distribution and level of disturbance. The study highlights the importance for managing deer of a balance between grazing and cover resources and the distribution of human disturbance.     

Prey selection and foraging performance of breeding Great Tits Parus major in relation to food availability

We studied the nestling diet and the foraging performance of Great Tits in relation to prey abundance in the field. Numerous experimental studies present data on foraging decisions in captive Great Tits. Little is, however, known about prey selection in the field in relation to the food available and the consequences this has for the food delivery rate to nestlings. Since the foraging performance of the parents is one of the main determinants of fledging weight and juvenile survival, foraging behaviour is an important part of Great Tit reproduction. During the early breeding season up to 75% of the prey biomass delivered to the nestlings were spiders, which is in contrast with other studies. Only when caterpillars reached a size of 10–12 mg (approximately the average size of the spiders caught at that time) did the Great Tits change their preferences and 80–90% of the delivered prey masses were caterpillars, as reported by other authors. This 'switching' between prey occurred within a few days. It was not related to the changes in abundance but to size of caterpillars. The rate at which caterpillars were delivered to the nestlings (in mg/nestling/h) was strongly correlated with the caterpillar biomass available (in mg/m of branches) and nestling growth rate was significantly influenced by the mass of available caterpillars. The results provide evidence why perfect timing of breeding is so important for the Great Tit, and contribute to the understanding of the causal link between food supply, growth and breeding success.     

Resource availability, breeding site selection, and reproductive success of red-winged blackbirds

Red-winged blackbirds are polygynous and show strong breeding site preferences, but it is unclear which environmental factors regulate their reproductive success and are ultimately responsible for shaping their patterns of habitat selection and their mating system. We evaluated the effect of variation in insect emergence rates on the reproductive success of male and female redwings nesting on replicate ponds. The number of male and female redwings that settled on a pond varied two- to three-fold among ponds, but was not related to insect emergence rates. Insect emergence rates had a positive effect on the number of nestlings successfully fledged by females, the number of nestlings fledged from male territories, and on the mass of nestlings at fledging. Typha stem density also varied widely among ponds, and was positively related to male and female settling density and mass of nestlings at fledging, but not to the number of nestlings fledged by females or males. We conclude that alternative breeding sites differ in their ability to support redwing reproduction, and that the availability of emerging odonates is an important environmental factor influencing the reproductive success of both male and female red-winged blackbirds. Received: 31 March 1997 / Accepted: 3 July 1997     

Diet composition and habitat selection of eland in semi-arid shrubland

This study investigated the diet composition and habitat selection of eland in semi-arid shrubland, dominated by microphyllous and leptophyllous browse species offering low leaf: stem ratios. Browse (succulent, forb and woody species) contributed 94% to the annual diet of eland. The annual proportion of grass in eland diet was low (6%), even though palatable grass species were abundant in habitats favoured by eland. Most grass was eaten in the early wet season when grasses offered young green foliage. Woody species comprising dwarf shrubs and shrubs made up the bulk of the food eaten by eland. In each season, favoured woody species contributed substantial proportions to the diet of eland. Eland used the plateau habitats in the early wet season, but valleys and slopes in the late wet and dry seasons. Habitats favoured by eland contained high abundances of plants of woody species favoured by eland. Chemical analysis indicated that woody species favoured by eland offered lower total fibre contents than other woody species available to eland. The results of the study indicated that eland are browsers that select browse of low fibre content.     

Pike predation affects breeding success and habitat selection of ducks

1. Fish and ducks often belong to the same local food web, and several studies indicate that there is a general negative effect of fish on breeding ducks. This pattern has so far been addressed mainly within the framework of competition for common invertebrate prey, while predation by large fish as a force behind settlement and abundance patterns in ducks remains largely unknown. This is the first study to address the effect of fish predation on breeding ducks, isolated from that of competition, and the first experiment to explore the ability of ducks to identify and avoid lakes with high risk of fish predation. 2. We used a before–after control–impact design and 11 naturally fishless lakes. Waterfowl on the lakes were surveyed during the breeding season of 2005. Large adult pike (Esox lucius) were added to two lakes in early spring 2008, and waterfowl surveys were repeated on all 11 lakes. 3. Pike introduction did not affect the number of pairs on lakes during the nesting season in any of three focal duck species (mallard Anas platyrhynchos, teal Anas crecca, and goldeneye Bucephala clangula). During the brood‐rearing season, however, there was a decrease in duck days in teal and goldeneye in lakes with pike, with similar trends observed in mallard. The number of goldeneye ducklings was also significantly lower in lakes with pike. We were unable to determine whether the response was attributable to direct pike predation or to broods leaving experimental lakes, but in either case, our study demonstrates high fitness costs for ducks breeding on lakes with pike. 4. The apparent inability of nesting ducks to detect pike and the clear fitness implications may influence the annual recruitment of ducks on a larger scale as pike are both common and widespread. Vegetation complexity and food abundance are likely to be of overriding importance when breeding ducks are choosing a nesting site. As pike have a strong influence on breeding birds, relying on vegetation and cues of food abundance, while ignoring indicators of predation risk from fish, could lead to lakes with pike acting as an ecological trap.     

Diet and food selection by Ramnogaster arcuata (Osteichthyes, Clupeidae)

The goals of this study were to describe the diet and estimate the trophic level and food selection of Jenyns's sprat Ramnogaster arcuata, one of the common fishes in the Bahía Blanca estuary in Argentina. The copepods Acartia tonsa [53·7% index of relative importance (I(RI))] and Eurytemora americana (13·4% I(RI)), the mysid Arthromysis magellanica (13·9%I(RI)) and the small shrimp Peisos petrunkevitchi (8·2% I(RI)) were the most important food items for this species, and its diet exhibited monthly variability with respect to the principal prey categories. The zooplankton species in the study area consisted of 32 taxa. Acartia tonsa was the most abundant species [54% individuals (N) m(-3)], followed by Balanus glandula (13·8% N m(-3)) and E. americana (10·1% N m(-3)). The rest of the zooplankton groups represented <3% N m(-3). The most preferred items throughout the year were A. magellanica and Idotea sp. The trophic level value estimated was 3·1.     

Conspecific cues and breeding habitat selection in an endangered woodland warbler

1.?Research on habitat selection has focused on the role of vegetative and geologic characteristics or antagonistic behavioural interactions. 2.?Conspecifics can confer information about habitat quality and provide positive density-dependent effects, suggesting habitat selection in response to the presence of conspecifics can be an adaptive strategy. 3.?We conducted a manipulative field experiment investigating use of conspecific location cues for habitat selection and consequent reproductive outcomes for the endangered golden-cheeked warbler (Setophaga chrysoparia). We investigated the response in woodlands across a range of habitat canopy cover conditions typically considered suitable to unsuitable and using vocal cues presented during two time periods: pre-settlement and post-breeding. 4.?Warblers showed a strong response to both pre-settlement and post-breeding conspecific cues. Territory density was greater than four times higher in treatment sample units than controls. The magnitude of response was higher for cues presented during the pre-settlement period. Positive response to conspecific cues was consistent even in previously unoccupied areas with low canopy cover typically considered unsuitable, resulting in aggregations of warblers in areas generally not considered potential habitat. 5.?Pairing and reproductive success of males was not correlated with canopy cover, as commonly thought. Pairing success and fledging success increased with increasing territory density suggesting that conspecific density may be more important for habitat selection decisions than the canopy cover conditions typically thought to be most important. These results suggest the range of habitat within which birds can perform successfully may be greater than is typically observed. 6.?Our results suggest the territory selection process may not be substantially influenced by competition in some systems. Settlement in response to conspecific cues produced aggregations within larger areas of similar vegetative characteristics. Understanding what cues drive habitat selection decisions and whether these cues are correlated with habitat quality is critical for conserving fitness-enhancing habitats, avoiding creation of ecological traps, generating accurate predictions of species distributions and understanding how occupancy relates to habitat suitability.     

Testing habitat copying in breeding habitat selection in a species adapted to variable environments

The habitat copying hypothesis states that animals use the reproductive performance of conspecifics to evaluate habitat quality and choose their future breeding site. We used data from Audouin's Gull Larus audouinii (1992–2003), a species adapted to unpredictable environments, to analyse subcolony (as patch) choice within a colony (small spatial scale). We also assessed the suitability of alternative hypotheses to the habitat copying hypothesis. The probability of subcolonies being reoccupied annually increased with their size (as number of nests), which suggests the existence of group adherence effects. Subcolony growth rate was related to its average reproductive success (or patch reproductive success) in the previous year: the higher the reproductive success in a colony, the higher the probability of growth the following year. However, this last result was obtained without considering the effect of colony size on the response variable because colony size is related to it. Therefore, results suggest at the population level that in this system habitat copying might either be one of the strategies used by the species in selecting its breeding habitat, or one of the possible strategies operating alone. The other strategies are group adherence mechanisms, and also the effect of conspecific attraction. At the individual level we failed to find evidence of habitat copying and only the previous success of an individual affected its fidelity to a subcolony. The importance of the lack of environmental predictability in the system is discussed, as predictability is a prerequisite of habitat copying.     

Dynamics of food availability, body condition and physiological stress response in breeding Black-legged Kittiwakes

1. The seasonal dynamics of body condition (BC), circulating corticosterone levels (baseline, BL) and the adrenocortical response to acute stress (SR) were examined in long-lived Black-legged Kittiwakes, Rissa tridactyla , breeding at Duck (food-poor colony) and Gull (food-rich colony) Islands in lower Cook Inlet, Alaska. It was tested whether the dynamics of corticosterone levels reflect a seasonal change in bird physiological condition due to reproduction and/or variation in foraging conditions.
2. BC declined seasonally, and the decline was more pronounced in birds at the food-poor colony. BL and SR levels of corticosterone rose steadily through the reproductive season, and BL levels were significantly higher in birds on Duck Island compared with those on Gull Island. During the egg-laying and chick-rearing stages, birds had lower SR on Duck Island than on Gull Island.
3. The results suggest that, in addition to a seasonal change in bird physiology during reproduction, local ecological factors such as food availability affect circulating levels of corticosterone and adrenal response to acute stress.     

Northern bobwhite breeding season habitat selection in fire-maintained pine woodland

Despite the acknowledged importance of prescribed fire in creating northern bobwhite (Colinus virginianus) breeding cover, little research has investigated bobwhite breeding season habitat selection relative to time since fire. In 2016 and 2017, we monitored radio-tagged bobwhite on a 17,000-ha portion of a military installation managed with frequent (every ~3 years) prescribed fires, applied during the growing and dormant seasons. We monitored bobwhite to determine which vegetation characteristics associated with prescribed burning were important to bobwhite breeding season habitat selection at the microsite (i.e., telemetry location compared to nearby random location) and the macrosite scale (i.e., the burn-unit containing the location compared to study area availability). During 2 breeding seasons, we collected 2,315 bobwhite locations and compared percent cover of vegetation, days since burn, basal area, and distance to key landscape features (e.g., stream, wildlife opening) at a subset of microsite locations (301 locations during 2016 and 890 locations during 2017) to paired random locations. At the microsite scale, bobwhite selected lower basal area of hardwoods, greater woody understory cover, greater other (not wiregrass [Aristida stricta]) grass cover, and greater forb cover than at random points. At the macrosite scale, bobwhite selected units with <4.6 m²/ha basal area (combined hardwoods and pines) in 2016 and units with <9.2 m²/ha basal area in 2017. At the macrosite scale, bobwhite selected for areas burned in the dormant season of the same year, avoided areas burned in the growing season of the same year, and used other times since last burn categories proportionate to their availability. The selection for a low basal area at both scales indicates prescribed fire effects would be limited by shading from dense overstory, and the shrubs, grasses, and forbs that provide essential cover for bobwhite during the breeding season will not develop. In lower productivity soil regions similar to our study area, we advise that thinning operations set target basal areas below 10 m²/ha to create and maintain breeding season habitat for northern bobwhite. © 2019 The Wildlife Society     

大鸨繁殖期觅食地的选择

2000年和2001年的4～7月,在内蒙古自治区科尔沁右翼前旗东南部的草原地带,采用样方法研究了火烧地和非火烧地上繁殖期大鸨的觅食地选择.结果表明,在火烧地和非火烧地,大鸨觅食地的植株高度均为13cm左右,最高高度不超过30cm,植被结构上具有共性;植物种类丰盛密集,盖度较大,喜食的植物和昆虫丰富.但在喜食食物选择上,火烧对大鸨有一定影响.在非火烧地,大鸨多关注动物性食物的丰盛;而在火烧地则关注植物性食物的丰盛.     

Dynamics of habitat distribution in breeding mallards: assessing the applicability of current habitat selection models

The applicability of ideal free, ideal despotic and ideal preemptive habitat selection models to explain dynamics of habitat distribution of breeding mallards ( Anas platyrhynchos ) was explored. Data from 35 lakes studied between 1985 and 2000 were used to examine overall habitat distribution of breeding pairs, breeding success in different habitats, within-year order of habitat occupation, and density dependence of habitat distribution and breeding success. Two habitat types, rich and poor, were defined based on the structure and luxuriance of shore vegetation; each lake belonged to one or the other of the habitat types. Breeding pairs used the rich habitat more than expected, breeding density also being higher there than in the poor habitat. Both average brood density and breeding success were higher in the rich habitat than in the poor. Breeding success was not density dependent, neither when analysed separately for the habitat types, nor in the study area in general. Within season, arriving mallard pairs did not occupy rich lakes earlier than poor lakes. An isodar analysis based on between-year variation of the breeding density in rich and poor habitats revealed that habitat distribution of breeding pairs was not density dependent. By contrast, density in the rich habitat increased and proportional use of the poor habitat decreased with increasing overall population density, i.e. the rich habitat got increasingly crowded. None of the habitat selection models considered was applicable to explain the dynamics of habitat distribution of breeding mallards.     

Shifts in breeding habitat selection behaviour in response to population density

We tested whether mountain pine beetles Dendroctonus ponderosae, an insect herbivore that exhibits outbreak population dynamics, modifies its habitat selection behaviour in response to density‐dependent environmental shifts. Using an individual‐based habitat selection model, we formulated predictions of how beetle population density will influence breeding habitat selectivity. Our model predicted that beetles should be more selective at intermediate densities than at low or high densities. The mechanisms influencing optimal selectivity differed between low and high density populations. In low density populations, breeding site availability was the primary factor affecting selectivity, whereas intraspecific competition and the reliability of habitat quality cues were important in high density populations. We tested our model predictions in natural populations that encompassed a range of beetle population densities. Our empirical findings supported the two key predictions from our model. First, habitat quality was more variable in high density populations. Second, individuals in high density populations were less selective compared to beetles from intermediate density populations. Our results demonstrate that beetles alter their habitat selection behaviour in response to density‐dependent shifts. We propose that the behavioural changes we identified may influence the rate at which beetle populations transition between density states.