Range sizes and habitat use of non‐breeding Crested Caracaras in Florida

In Florida, habitats that include the breeding territories of Crested Caracaras (Caracara cheriway) are protected, but non‐breeding individuals may be vulnerable because they may occupy different areas and habitats. We captured and radio‐tagged 58 non‐breeding caracaras in Florida from July 2006–March 2009, determined their locations during weekly flights, and used GIS and compositional analysis to evaluate range sizes and habitat use. Non‐breeding caracaras (N = 58) ranged five times more widely during breeding seasons (N = 573 locations) than during non‐breeding seasons (N = 592 locations), and ranged >250 times more widely than breeding caracaras that defend territories year‐round. The large ranges of non‐breeders suggest they may be searching for and evaluating prospective territories or breeding opportunities (territory prospecting). Pasture occupied by cattle was the most used habitat relative to availability and was used more than pasture without cattle, likely because insects associated with cattle are an important food source for caracaras. Cattle numbers in Florida are declining and, because both breeding and non‐breeding caracaras primarily occupy pasture, this may present difficulties for long‐term management. Citrus groves were also used more than expected given availability by non‐breeding caracaras, but are rarely included in nesting territories. Because pasture and citrus were often adjacent, we suggest that citrus groves may function as refugia from socially dominant breeding caracaras. Conservation and recovery efforts for Florida's caracara population are needed throughout the range of non‐breeders, and should include management that ensures availability of habitat matrices of cattle pasture and citrus groves.     

Factors influencing the nesting success of Lapwings Vanellus vanellus and behaviour of Red Fox Vulpes vulpes in Lapwing nesting sites

Capsule Lapwing nest predation was negatively correlated to nest density, while Lapwing alarm duration in response to foxes was positively correlated with the number of Lapwing broods present.

Aims To identify factors affecting Lapwing nest predation and Red Fox search effort.

Methods Lapwing nest success was monitored at four sites in 1996, seven sites in 1997 and six sites in 1998. In 1997 we mapped the position of all Lapwing nests in order to determine distances between nests, and the proximity of linear features and potential avian predator perches to each nest. From April to June 1998 we carried out 199 hours of nocturnal observations at six Lapwing nesting sites using night vision equipment.

Results The risk of nest predation was significantly higher for more isolated nests. Nocturnal observations showed that of all the nocturnal predators, foxes were the most active at Lapwing nesting sites. However, fox search effort in Lapwing colonies was relatively low, averaging 57 s/ha per visit. Foxes spent significantly longer foraging near breeding Lapwings (measured as duration of alarm calls) when more broods were present. Fox search effort (s/ha per hour of observation) tended to be greater in areas of high waterbird density.

Conclusion The lack of positive density-dependent nest predation, the relatively low search effort of foxes near Lapwing nesting sites and the high nest success sometimes achieved in areas with foxes all suggest that Lapwing nest predation by foxes is ‘incidental’. Lapwing chicks are probably more vulnerable to predation by foxes than clutches.     

Environmental Factors Affecting Productivity of Brown-Headed Nuthatches

Abstract: Understanding the link between habitat use and components of fitness can yield useful insight into the environmental conditions necessary for population maintenance and can help promote effective habitat management. This information is especially important for species that are in decline or otherwise of conservation concern. Populations of brown-headed nuthatches (Sitta pusilla), an obligate cavity nester, have declined throughout their range, primarily due to extensive habitat loss and degradation. To help guide habitat management for this species, we identified habitat features associated with variation in the number of offspring fledged within 2 populations in southern Florida, USA. The most important predictor of productivity was the date on which a nest attempt began, with earlier nests producing more fledglings. The number of large pine (Pinus elliottii var. densa) snags and, to a lesser extent, the number of small pine trees surrounding a nest site were positively associated with productivity. We recommend that land managers in southern Florida focus on providing abundant large pine snags because doing so will increase productivity and also may increase nest-site availability and the percentage of individuals that breed each year. Prescribed burning may be an effective way to increase the abundance of large pine snags; however, land managers should exercise caution when doing so because of the trade-off between snag recruitment and snag consumption that accompanies the use of fire. We lack the data required to predict the fire-return interval that optimizes this trade-off, but until these data are available we recommend increasing the spatial heterogeneity in fire-return interval and lengthening the fire-return interval in some areas to 5-6 years.     

The impact of researcher disturbance on nest predation rates: a meta‐analysis

The effects of visits to nests by researchers interested in quantifying avian nesting success have received considerable attention, as researchers have long been concerned about the possible negative effects of their own activities on the resulting estimates. There is a widely held view that investigator disturbance has an overall negative effect on breeding success by increasing nest predation rates in the nests studied. However, to date no one has statistically assessed the empirical evidence for such a relationship. We undertook a meta‐analysis of published results to assess whether researcher activities increase nest predation in birds. We also assessed the variability in this effect in relation to the traits of the study species and the methodology used. These analyses used data from 18 experimental studies involving 25 species from six avian orders. Our results suggest that, contrary to the traditional view, researcher activities do not generally affect the incidence of nest predation. Moreover, this relationship appears inconsistent among avian orders and, surprisingly, nest survival of passerines increased weakly with researcher activities. We also found significant positive effects of researcher activity on nest survival for species breeding on coastal areas and for species nesting on the ground. The possible explanation for these differences among orders and guilds could be due to different nest predator communities. This new perspective on the effect of investigators could have important implications for bird management and conservation, as well as for other fields of study such as ecology and evolution, in which nest survival rates measured in the field are widely used to test and support a range of hypotheses.     

Factors influencing the efficiency of a marker-assisted introgression programme in Merino sheep

This study investigated a marker-assisted introgression programme in Australian Merino sheep. The goal was to introgress an allele with a large negative effect on fibre diameter into a Merino flock possessing medium average fibre diameter. The influence of two factors was explored: the strategy used to select animals from the purebred and backcross line for backcrossing purposes and the use of selection on background markers to accelerate the return to the purebred line''s genome. The results were compared to introgression based on EBVs only. Introgression using EBVs only produced almost the same response in the dollar index as marker-based introgression methods. However, this study did not account for some of the costs associated with implementing the programmes, including the costs of phenotyping and genotyping. Given that the cost of measuring fibre diameter is low, it was concluded that introgression on EBVs only would be the preferred method since the marginal profit of marker-assisted introgression would not be large enough to cover the additional cost of genotyping. In marker-assisted introgression, reciprocal crossing of male and female selection candidates from the backcross and the purebred line was the most advantageous strategy from a practical and profit point of view. Selection for background markers was less profitable in this study than recovering the donor genome by selection on phenotype.     

Factors affecting spontaneous vocal activity of Tawny Owls Strix aluco and implications for surveying large areas

To use vocalizations properly for the estimation of owl population size, it is important to identify how environmental factors affect owl calling behaviour. Here, we analyse how intrinsic and extrinsic factors modify the vocal activity of Tawny Owls Strix aluco in two areas of northern Spain. From March 2013 to May 2015, we radiotracked 20 Tawny Owls and also undertook a systematic survey in which we collected data on spontaneous vocal activity (hoot/call) of the tagged owls, plus their mates and neighbours (36 untagged owls). After 223 nights in Valle de Mena and 224 in Duranguesado we obtained a total of 8791 records of vocal activity. The annual proportion of surveys on which an owl called was 6.3% and did not differ between the study areas. Vocal activity of Tawny Owls varied with sex, annual cycle stage and weather. Male owls were significantly more vocal than females year‐round, and vocal activity peaked during the incubation and post‐breeding periods. Wind and rain adversely affected vocal activity of both sexes throughout the year. Tagged owls were detected more often than untagged owls, which we interpret as an observer effect because the systematic survey ensured that short distances to tagged owls increased the probability of detecting vocal activity. In fact, 2.8% of variation in vocal activity was due to detectability differences between tagged and untagged owls. We conclude that if fieldwork is carried out during the optimum period of the year for vocal detection (i.e. incubation, which in our case was around mid‐April), and under good weather conditions (dry and calm nights), censuses based on spontaneous vocal activity would detect only approximately 12% of the true Tawny Owl population.     

Habitat selection of nesting and fledgling salt marsh songbirds in northeast Florida

Understanding habitat selection by breeding birds and their newly fledged young can be an essential aspect of the conservation of vulnerable species. During 2015–2017, we examined nest site selection of Worthington's marsh wren (Cistothorus palustris griseus) and MacGillivray's seaside sparrow (Ammospiza maritima macgillivraii), and fledgling habitat use by Worthington's marsh wren, 2 imperiled species in northeast Florida, USA. We compared vegetation at unused points to vegetation at nests of both subspecies and at locations used by radio-tagged marsh wren fledglings. Vegetation was taller and stem counts were greater at nest sites compared to unused points. Worthington's marsh wrens also used nest sites with a greater proportion of tall-form smooth cordgrass (Spartina alterniflora) than was observed at unused points. Worthington's marsh wren fledglings also used locations with taller, denser vegetation, but vegetation use changed with fledgling age and tidal stage; older fledglings more frequently used areas with short-form smooth cordgrass and bare ground (and more so during low tides). In contrast, so few nests and nestlings were in black needlerush (Juncus roemerianus) that we could not consider it in our analysis despite its prevalence within our study sites. Our results indicate that tall, dense cordgrass is an important habitat component for these subspecies during the nesting and fledgling life stages in southeastern Atlantic salt marshes.     

Factors influencing detection of density dependence in British birds

If censuses are taken at less than generation intervals, the number of successive censuses in which a given individual is recorded will depend on longevity. Repeatedly recording the same individuals could produce under-estimates of population variability and influence detection of density dependence. We investigated this possibility in 60 time series of abundances of British birds compiled from the Common Birds Census data and then used simple population models to illustrate the proposed mechanism. Species had average lifespans of 2–10 years and were censused annually. Density dependence was detected (at P<0.05) much more frequently in bird species with long lifespans than in those with short lifespans; 75% of the 12 longest-lived species showed density dependence compared to 46% of all species. Population variability measured in annual censuses (termed annual variability) was lower in bird species with longer lifespans. We used discrete time models based on difference equations to demonstrate how longevity influences population variability and detection of density dependence in series of annual censuses. A model in which only first-year birds experienced density dependence was rejected because annual variability was greater and detection of density dependence was less likely when longevity was greater, the opposite of the observed effects of longevity in birds. A model in which all age classes experienced density dependence gave time series with lower annual variability and in which density dependence was detected more frequently when longevity was greater, which is the pattern observed in British birds. Analysis of data from this model showed that the amount of density dependence actually present caused only small changes in annual variability, whereas detection of density dependence from simulated series was strongly influenced by annual variability. The high annual variability of series from short-lived bird species could mask any density dependence that was present. Correcting for trends lead us to detect density dependence in 75% of the 12 longest lived bird species. There is no reason to believe that this rate is not also representative of short-lived species.     

Factors affecting detection probability of burrowing owls in southwest agroecosystem environments

Estimating range-wide population trends of western burrowing owls (Athene cunicularia) requires standardized survey protocols that correct for detection bias in environments that support large owl populations. High concentrations of owls exist in irrigated agroecosystems within the southwest United States, yet little is known about the factors that affect detection bias during owl surveys in these systems. I used closed-population capture-recapture models to evaluate 4 factors that could affect the probability of a surveyor detecting an owl activity center (i.e., nest burrow) during visual surveys where owls are the focal object and analyzed the relationship (linear or curvilinear) between specific factors and detection probability. I recorded 1,199 detections of owls from 132 capture-recapture surveys within 12 sites of the Imperial Valley agroecosystem in California, USA between 16 April and 20 May 2006. I also conducted 96 time budget surveys throughout the day and used mixed linear models to evaluate the effect of each factor on probability of an owl activity center being available for detection (i.e., ≥1 owls above ground) during surveys. Model selection results indicated that detection probability was influenced by ambient air temperature interacting with wind speed. Detection probability followed a curvilinear relationship that resembled bell-shaped curve along a temperature gradient, with the maximum detection probability shifting as a function of wind speed. At low temperatures, detection probability declined with increased wind speed, but this relationship was reversed at high temperatures, producing a 3-dimensional pattern in detection probability characterized by a saddle-shaped hyperbolic paraboloid response surface. The probability of an activity center being available for detection declined curvilinearly with increased temperature and explained 51% of the variation in detection probability. Given the broad range of detection probabilities, correcting visual survey counts for detection bias is necessary for comparing population estimates among regions and through time. Survey designs intended to estimate abundance of owls in southwest agroecosystems should incorporate methods to estimate and correct for variation in detection probability that include measurements of ambient temperature and wind speed for use as covariates. © 2011 The Wildlife Society.     

Factors affecting nesting success in the Great-crested Grebe Podiceps cristatus at Lake Tonga,north-east Algeria

The breeding ecology of the Great-crested Grebe Podiceps cristatus was investigated over four consecutive years (2009-2012) at Lake Tonga, north-east Algeria. In all four years, the egg-laying period was relatively short, spanning two months (end of March to end of May), and bimodal. Nests were mainly located in Phragmites australis, over water of substantial depth (178 ± 43?cm, N=209), far from the shore and in habitat with low vegetation cover (12.37 ± 7.67%, N=209). The overall clutch size was 3.73 ± 0.92 eggs (N=127) and it decreased marginally over time. The overall nesting success was 70.4% (N=209), with nest failure caused mainly by predation (65%) and flooding (23%). Breeding outcome was significantly and positively related to nest size, with bigger nests conferring better survival to eggs and young probably through affording better protection during spells of adverse weather. However, the benefits of bigger nests may be confounded by the age or intrinsic quality of birds. The location of nests in P. australis, rather than other vegetation types, increased nesting success marginally but significantly. Two cases of interspecific mixed clutches involving the Great-crested Grebe were recorded.     

灰胸薮鹛繁殖行为初报

2009年春季在四川省屏山县老君山自然保护区对灰胸薮鹛Liocichla omeiensis繁殖行为进行了观察.灰胸薮鹛胆小畏人,喜藏匿于茂密灌丛中活动、鸣叫.4月中旬进入繁殖期后雄鸟占区鸣唱逐渐增加,5月中旬占区鸣唱达到高峰,5月下旬逐渐减少,进入育雏期.在山顶茂密方竹丛中找到1巢,对其进行了2个全天观察,雌、雄鸟共同喂雏,亲鸟均会暖雏,但雄鸟暖雏较雌鸟少.亲鸟吃掉幼鸟粪便及食物残渣,以保持巢的清洁.亲鸟喂给幼鸟食物以昆虫和小型蛾类为主,在巢期为15天.     

Use of farmland by Ortolan Buntings (Emberiza hortulana) nesting on a burned forest area

Summary Most passerines have all-purpose territories in which both breeding and feeding take place. However, Ortolan Buntings (Emberiza hortulana) in Norway seem to depend on foraging areas outside nesting territories. We used radio transmitters to study patterns of farmland use by Ortolan Buntings nesting on a burned forest area. Territories on the forest burn were located closer to farmland than expected by chance. Males were absent from territories on average 27 % of the time and used foraging areas up to 2.7 km away from their territories. Males had to fly over an average of 1.4 territories of other males to reach those foraging areas. The distance between territory and closest area of farmland (range 40–460 m) did not affect the proportion of time absent from territories, or other measures of farmland use. However, there was a trend that duration of absences increased with territory-farmland distance among mated males, and duration of absences were shorter during the nestling period than before. Thus, it seems that minimizing travel costs may be a behavioural strategy. Even so, males with territories close to farmland were not more often paired than males further away from farmland. These findings indicate that the spatial distribution of one habitat (farmland) affects territory establishment and foraging behaviour of Ortolan Buntings nesting in another habitat (a forest burn).

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Nutzung von Ackerland durch Ortolane (Emberiza hortulana) einer benachbarten Brandfl?che

Zusammenfassung Bei den meisten Singv?geln ist das Revier sowohl Brut- als auch Nahrungsraum. Bei Ortolanen (Emberiza hortulana) in Norwegen, die auf Brandflachen brüten, scheint dies aber anders zu sein. Radiotelemetrische Untersuchen zeigten, dass sie von Nahrungsgründen au?erhalb der Brutterritorien abh?ngig sind. Die Nester auf den Brandflachen h?uften sich am Rand zum benachbarten Ackerland. M?nnchen waren durchschnittlich 27 % der Zeit vom Brutrevier abwesend und gingen his zu 2,7 km vom Brutplatz entfernt auf Nahrungssuche, wozu sie durchschnittlich 1,4 Reviere anderer M?nnchen überfliegen mussten. Der Abstand zwischen Brutrevier und n?chstem Nahrungsplatz (zwischen 40 und 460 m) hatte keinen Einfluss auf den Zeitanteil au?erhalb des Brutreviers. Die Dauer der Abwesenheit stieg jedoch bei verpaarten M?nnchen mit der Entfernung zwischen Brutrevier und Ackerland und sie war kürzer w?hrend der Nestlingsphase. Dies wird als Verhaltensstrategie zur Minimierung der Flugkosten interpretiert. M?nnchen mit Revieren n?her am Ackerland waren nicht h?ufiger verpaart als mehr entfernte Revierinhaber. Diese Untersuchungen zeigen, dass beim Ortolan die r?umliche Verteilung eines Habitats (hier Ackerland) einen Einfluss auf die Etablierung von Brutrevieren und das Nahrungssuchverhalten in einem anderen Lebensraum (hier Brandfl?chen) hat.

     

Using species distribution models to define nesting habitat of the eastern metapopulation of double‐crested cormorants

When organisms with similar phenotypes have conflicting management and conservation initiatives, approaches are needed to differentiate among subpopulations or discrete groups. For example, the eastern metapopulation of the double‐crested cormorant (Phalacrocorax auritus) has a migratory phenotype that is culled because they are viewed as a threat to commercial and natural resources, whereas resident birds are targeted for conservation. Understanding the distinct breeding habitats of resident versus migratory cormorants would aid in identification and management decisions. Here, we use species distribution models (SDM: Maxent) of cormorant nesting habitat to examine the eastern P. auritus metapopulation and the predicted breeding sites of its phenotypes. We then estimate the phenotypic identity of breeding colonies of cormorants where management plans are being developed. We transferred SDMs trained on data from resident bird colonies in Florida and migratory bird colonies in Minnesota to South Carolina in an effort to identify the phenotype of breeding cormorants there based on the local landscape characteristics. Nesting habitat characteristics of cormorant colonies in South Carolina more closely resembled those of the Florida phenotype than those of birds of the Minnesota phenotype. The presence of the resident phenotype in summer suggests that migratory and resident cormorants will co‐occur in South Carolina in winter. Thus, there is an opportunity for separate management strategies for the two phenotypes in that state. We found differences in nesting habitat characteristics that could be used to refine management strategies and reduce human conflicts with abundant winter migrants and, at the same time, conserve less common colonies of resident cormorants. The models we use here show potential for advancing the study of geographically overlapping phenotypes with differing conservation and management priorities.     

Nest monitoring does not affect nesting success of Whinchats Saxicola rubetra

It is important to assess the effect that research activities may have on animals in the wild, especially when key parameters, such as breeding success, could potentially be influenced by observer activity. For birds, some studies have suggested that nest monitoring can increase the chances of nest failure due to predation, whereas others suggest that human nest visits may actually deter mammalian predators. Nest monitoring visits can also influence breeding success more indirectly by altering parental provisioning behaviour. Here, the influence of monitoring activities on nest success was examined in a ground‐nesting grassland bird, the Whinchat Saxicola rubetra. During the egg phase, a sample of nests were not visited between the initial finding event and the estimated hatching date; instead, the nest status was assessed at a distance. Daily survival rates (DSR) for these nests were compared with that of nests visited every 2 days. During the nestling phase, the effects of observer nest visits on parental provisioning behaviour were determined. Nest visits were found not to affect egg DSR significantly, and parental provisioning was disrupted for a maximum of 20 min (0.52% of the nestling period) following an observer visit. Given the variation in response to nest visits across species, we suggest that consideration should be given to observer impact in all studies where predation risk is high. Here, we illustrate a method for researchers to assess the impact of their nest visits to ensure they are not biasing estimates of breeding success.     

Factors influencing detection of eDNA from a stream‐dwelling amphibian

Environmental DNA (eDNA) methods for detecting and estimating abundance of aquatic species are emerging rapidly, but little is known about how processes such as secretion rate, environmental degradation, and time since colonization or extirpation from a given site affect eDNA measurements. Using stream‐dwelling salamanders and quantitative PCR (qPCR) analysis, we conducted three experiments to assess eDNA: (i) production rate; (ii) persistence time under different temperature and light conditions; and (iii) detectability and concentration through time following experimental introduction and removal of salamanders into previously unoccupied streams. We found that 44–50 g individuals held in aquaria produced 77 ng eDNA/h for 2 h, after which production either slowed considerably or began to equilibrate with degradation. eDNA in both full‐sun and shaded treatments degraded exponentially to <1% of the original concentration after 3 days. eDNA was no longer detectable in full‐sun samples after 8 days, whereas eDNA was detected in 20% of shaded samples after 11 days and 100% of refrigerated control samples after 18 days. When translocated into unoccupied streams, salamanders were detectable after 6 h, but only when densities were relatively high (0.2481 individuals/m²) and when samples were collected within 5 m of the animals. Concentrations of eDNA detected were very low and increased steadily from 6–24 h after introduction, reaching 0.0022 ng/L. Within 1 h of removing salamanders from the stream, eDNA was no longer detectable. These results suggest that eDNA detectability and concentration depend on production rates of individuals, environmental conditions, density of animals, and their residence time.     

Thermal characteristics of wild and captive Micronesian kingfisher nesting habitats

To provide information for managing the captive population of endangered Guam Micronesian kingfishers (Halcyon cinnamomina cinnamomina), four biologically relevant thermal metrics were compared among captive facilities on the United States mainland and habitats used by wild Micronesian kingfishers on the island of Pohnpei (H. c. reichenbachii), Federated States of Micronesia. Additionally, aviaries where kingfishers laid eggs were compared to those in which birds did not attempt to breed. Compared to aviaries, habitats used by wild Pohnpei kingfishers had 3.2°C higher daily maximum and minimum temperatures and the proportion of time when temperatures were in the birds' thermoneutral zone was 45% greater. No differences were found in the magnitude of temperature fluctuation in captive and wild environments. In captive environments in which birds bred, daily maximum temperatures were 2.1°C higher and temperatures were within the thermoneutral zone 25% more often than in the aviaries where the kingfishers did not breed. No differences were found in the magnitude of temperature fluctuation or the daily minimum temperature. Results suggest that the thermal environment has the potential to influence reproduction, and that consideration should be given to increasing temperatures in captive breeding facilities to improve propagation of the endangered Micronesian kingfisher. Zoo Biol 23:301–308, 2004. Published 2004 Wiley‐Liss, Inc.