Distance Of Birds Research Articles

Morphological adaptations linked to flight efficiency and aerial lifestyle determine natal dispersal distance in birds

Abstract Natal dispersal—the movement from birthplace to breeding location—is often considered the most significant dispersal event in an animal's lifetime. Natal dispersal distances may be shaped by a variety of intrinsic and extrinsic factors, and remain poorly quantified in most groups, highlighting the need for indices that capture variation in dispersal among species. In birds, it is hypothesized that dispersal distance can be predicted by flight efficiency, which can be estimated using wing morphology. However, the use of morphological indices to predict dispersal remains contentious and the mechanistic links between flight efficiency and natal dispersal are unclear. Here, we use phylogenetic comparative models to test whether hand‐wing index (HWI, a morphological proxy for wing aspect ratio) predicts natal dispersal distance across a global sample of 114 bird species. In addition, we assess whether HWI is correlated with flight usage in foraging and daily routines. We find that HWI is a strong predictor of both natal dispersal distance and a more aerial lifestyle. Our results support the use of HWI as a valid proxy for relative natal dispersal distance, and also suggest that evolutionary adaptation to aerial lifestyles is a major factor connecting flight efficiency with patterns of natal dispersal. Read the free Plain Language Summary for this article on the Journal blog.

Limited-Distance Pollen Dispersal and Low Paternal Diversity in a Bird-Pollinated Self-Incompatible Tree.

Bird pollination in Asia is regarded as an uncommon phenomenon and, therefore, only a few investigations on mating pattern and paternity in fruits of Asian bird-pollinated plants have been conducted. Here, we examined spatial genetic structure, pollen dispersal, and multiple paternity in a natural population of Bombax ceiba (B. ceiba) (Malvaceae) in Hainan Island, South China, using simple sequence repeat (SSR) markers. A low genetic diversity (He = 0.351 ± 0.0341 and 0.389 ± 0.043, respectively, for adults and offspring) and bottleneck effects were observed. Genetic kinship was significant within 400 m or in 1,800–3,800 m. Both the mating pattern and paternity analysis confirmed obligate xenogamy and a low multiple paternity in B. ceiba. There was a strongly negative relationship between the frequency of matings and the distance between mating pairs. The average pollen dispersal distance was 202.89 ± 41.01 m (mean ± SE) and the farthest distance of > 1 km was recorded. Realized mating events showed an extremely leptokurtic distribution within 1,200 m, suggesting that the pollen dispersal distance was consistent with the optimal foraging theory of generalist birds such as Zosterops spp. and Pycnonotus spp. Paternity per tree ranged from two to six and the average effective number of pollen donors per maternal plant was 3.773, suggesting a low level of paternity diversity as compared to other bird-pollinated plants. We concluded that optimal foraging behavior by generalist birds could explain the leptokurtic pollen dispersal distribution and predominantly near-neighbor matings in B. ceiba. The limited pollen dispersal distance and low multiple paternity were consistent with low fruit setting rate (3.27 ± 0.93%) in this self-incompatible tree, which was caused mainly by the restricted flight distance of birds and human disturbances. Low genetic diversity and significant spatial genetic structure might have largely resulted from logging and human collection of fruits.

Динаміка популяцій воронових і їхній вплив на мисливську фауну Луганської області

Досліджено багаторічну (1983–2013 рр.) динаміку щільності популяцій птахів родини Воронових (Corvidae) у мисливських угіддях Щетівського лісництва Іванівського ДЛМГ Луганської області. Щільність популяцій визначено методом маршрутного обліку без обмеження смуги огляду та перераховувано на 1 км2 за середньою дальністю виявлення птахів. Встановлено, що за 30 років щільність популяції ворона в регіоні досліджень збільшилася в 11,5 раза – від 0,1 до 1,15 екз./км2, щільність популяції ворони сірої зменшилася в 11,1 раза – від 3,4 до 0,3 екз./км2, сороки – у 2,4 раза, граків і галок – у 9,2 та 2 рази відповідно, сойки – в 1,6 раза. Визначено тісний від'ємний зв'язок між щільністю популяцій ворона та інших досліджених видів воронових, найтісніший – між щільністю популяцій ворона та ворони сірої, з огляду на близьку екологію цих двох видів із перевагами ворона як більш великого та агресивного виду. Проаналізовано залежність щільності популяцій ворона, ворони сірої, сороки, грака, галки та сойки від особливостей живлення, місць поселення, шкоди для об'єктів полювання та антропогенних чинників (зміни системи обробітку ґрунту, структури посівних площ, ліквідації тваринницьких комплексів тощо). Рекомендовано спростити одержання дозволів на відстріл ворона, який завдає великої шкоди об'єктам полювання (крижню та іншим качкам, фазану, куріпці сірій та зайцю-русаку).

Relating flight initiation distance in birds to tropical dry forest restoration

Flight initiation distance (FID), defined as the distance at which an individual flees from an approaching predator, might depend on how the individual perceives the risk of being predated. Using a standardized walking approach method on focal bird individuals, we investigated whether different levels of vegetation cover (habitat) influence the perception of predation risk. To do this, we worked in an area of tropical dry forest in central Mexico that is currently part of a restoration ecology experiment. We hypothesized that restoration decreases individual’s predation risk perception by increasing the complexity of the vegetation cover. The escape responses of three tropical birds with different diets and foraging strategies were also contrasted. There was no effect of habitat on FID, suggesting that birds in both habitats perceived predation risk in a similar manner. There was, however, a difference in FID among species: the Golden-cheeked Woodpecker tolerated closer human presence before flight than the Inca Dove and Streak-backed Oriole. This difference is likely due to the use of an alternative avoidance strategy of this species, which uses trunks for hiding. To decrease birds’ perceived predation risk, restoration intervention plans should include a mosaic of larger excluded plots located near relatively well-conserved sites to increase the area covered by vegetation.

Comparison of acoustic recorders and field observers for monitoring tundra bird communities

ABSTRACTAcoustic recorders can be useful for studying bird populations but their efficiency and accuracy should be assessed in pertinent ecological settings before use. We investigated the utility of an acoustic recorder for monitoring abundance of tundra‐breeding birds relative to point‐count surveys in northwestern Alaska, USA, during 2014. Our objectives were to 1) compare numbers of birds and species detected by a field observer with those detected simultaneously by an acoustic recorder; 2) evaluate how detection probabilities for the observer and acoustic recorder varied with distance of birds from the survey point; and 3) evaluate whether avian guild‐specific detection rates differed between field observers and acoustic recorders relative to habitat. Compared with the observer, the acoustic recorder detected fewer species (βMethod = −0.39 ± 0.07) and fewer individuals (βMethod = −0.56 ± 0.05) in total and for 6 avian guilds. Discrepancies were attributed primarily to differences in effective area surveyed (91% missed by device were >100 m), but also to nonvocal birds being missed by the recorder (55% missed <100 m were silent). The observer missed a few individuals and one species detected by the device. Models indicated that relative abundance of various avian guilds was associated primarily with maximum shrub height and less so with shrub cover and visual obstruction. The absence of a significant interaction between survey method (observer vs. acoustic recorder) and any habitat characteristic suggests that traditional point counts and acoustic recorders would yield similar inferences about ecological relationships in tundra ecosystems. Pairing of the 2 methods could increase survey efficiency and allow for validation and archival of survey results. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Possible linkage between neuronal recruitment and flight distance in migratory birds.

New neuronal recruitment in an adult animal’s brain is presumed to contribute to brain plasticity and increase the animal’s ability to contend with new and changing environments. During long-distance migration, birds migrating greater distances are exposed to more diverse spatial information. Thus, we hypothesized that greater migration distance in birds would correlate with the recruitment of new neurons into the brain regions involved with migratory navigation. We tested this hypothesis on two Palearctic migrants - reed warblers (Acrocephalus scirpaceus) and turtle doves (Streptopelia turtur), caught in Israel while returning from Africa in spring and summer. Birds were injected with a neuronal birth marker and later inspected for new neurons in brain regions known to play a role in navigation - the hippocampus and nidopallium caudolateral. We calculated the migration distance of each individual by matching feather isotopic values (δ2H and δ13C) to winter base-maps of these isotopes in Africa. Our findings suggest a positive correlation between migration distance and new neuronal recruitment in two brain regions - the hippocampus in reed warblers and nidopallium caudolateral in turtle doves. This multidisciplinary approach provides new insights into the ability of the avian brain to adapt to different migration challenges.

Factors affecting escape distance in birds

The flight initiation distance has been used either to understand the cost-benefit trade-offs related to the risk of predation or as an important tool for wildlife managers. Although this variable is well-discussed for temperate regions, it is still poorly known in the Neotropics. Here we analyze the escape behavior of birds from southeastern Brazil, comparing an urban to a non-urban area. We tested for the influence of sites (urban vs. non-urban area), approaching (by one vs. two people), daytime (morning vs. afternoon), seasons (breeding vs. non-breeding) and body mass on the determination of the initial (FID) and final (FFD) flight distances across different bird species. We predict that FID will be greater in rural areas and under a greater threat (higher number of predators approaching) in the afternoon and in the non-breeding season. We also expect a direct relationship between body mass and FID and between FID and FFD. We sampled 11 species after measuring 331 escape behaviors, and we confirmed our predictions for sites (five species), daytime (one species) and rejected our premise about seasons for one species. Mean FID was strongly affected by body mass, and directly affected FFD. Adjustments in FID are, most likely, an important adaptive trait in urban habitats and may partially explain the predominance of species with higher ecological plasticity in cities.

A novel methodology for the rapid assessment of waterbird vulnerability to disturbance

A methodology for rapidly assessing the vulnerability of waterbirds to disturbance was tested at Sabaki estuary, Kenya. Three variables were employed to measure the responses of 15 species: (1) bird density, (2) minimum distance of birds from a stationary disturbance and (3) recovery times following a moving disturbance. Spatial response metrics (1) and (2) were regressed against expected species densities (in the absence of disturbance). Normalised mean residuals then described species-specific deviations from the average spatial response to disturbance. A hypothetical model was constructed, whereby species were placed on a spatial response gradient and overlaid by the recovery metric (3). Greater Flamingo Phoenicopterus roseus, Lesser Flamingo Phoeniconaias minor, African Spoonbill Platalea alba and Terek Sandpiper Xenus cinereus exhibited the strongest avoidance responses. The two spatial metrics (1 and 2) achieved concordance for 73% of species, and all three metrics gave similar results for six of seven species at the extremes of the spatial response gradient. Non-concordance between response metrics is likely an effect of life-history traits (e.g. territoriality). Our results support the use of relative spatial response metrics (1 and 2) for robust and rapid identification of waterbird species that are most responsive and, by virtue, vulnerable to the effects of disturbance on tropical estuaries.

Topography drives migratory flight altitude of golden eagles: implications for on‐shore wind energy development

Summary Wind power is a fast‐growing industry with broad potential to impact volant wildlife. Flight altitude is a key determinant of the risk to wildlife from modern horizontal‐axis wind turbines, which typically have a rotor‐swept zone of 50–150 m above the ground. We used altitudinal GPS data collected from golden eagles Aquila chrysaetos tracked using satellite telemetry to evaluate the potential impacts of wind turbines on eagles and other raptors along migratory routes. Eagle movements during migration were classified as local (1–5 km h−1) or migratory (>10 km h−1) and were characterized based on the type of terrain over which each bird was flying, and the bird's distance from wind resources preferred for energy development. Birds engaged in local movements turned more frequently and flew at lower altitude than during active migration. This flight behaviour potentially exposes them to greater risk of collision with turbines than when engaged in longer‐distance movements. Eagles flew at relatively lower altitude over steep slopes and cliffs (sites where orographic lift can develop) than over flats and gentle slopes (sites where thermal lift is more likely). Eagles predominantly flew near to wind resources preferred by energy developers, and locally moving eagles flew closer to those wind resources with greater frequency than eagles in active migration. Synthesis and applications. Our research outlines the general effects of topography on raptor flight altitude and demonstrates how topography can interact with raptor migration behaviour to drive a potential human–wildlife conflict resulting from wind energy development. Management of risk to migratory species from industrial‐scale wind turbines should consider the behavioural differences between both locally moving and actively migrating individuals. Additionally, risk assessment for wind energy–wildlife interactions should incorporate the consequences of topography on the flight altitude of potentially impacted wildlife.

Extreme Endurance Migration: What Is the Limit to Non-Stop Flight?

Migratory birds have a history of challenging conventional wisdom about the limits of their endurance. More than half a century ago, many ornithologists doubted that a non-stop flight of 860 km across the Gulf of Mexico was possible for migratory (humming) birds [1]. But circumstantial and more direct evidence gathered in the following decade revealed that the Gulf of Mexico is a mere ditch to migratory birds [2],[3], and that some are capable of non-stop flights of up to 5,000 km [4],[5]. And now migratory birds have given their observers reason to pause yet again. In the past year, Gill et al. [6] have provided direct evidence that a shorebird, the Alaskan bar-tailed godwit (Limosa lapponica baueri) (Figure 1), makes its eight-day, 11,000-km autumn migration from Alaska to New Zealand in one step, with no stopovers to rest or refuel. This roughly doubles the previous maximum direct flight distance in birds, challenging experts to square this remarkable marathon migration with our understanding of aerodynamic theory and endurance physiology. Figure 1 Bar-tailed godwits. Has this bird finally shattered the limits of long-distance, nonstop migratory flights, forcing researchers to rethink their theories and assumptions about flight and endurance? Or is it possible to show that such feats are possible given what we already understand about aerodynamic theory, metabolism, navigation, and evolution? Here I argue that we already have the tools in hand to understand how it can fly such a distance. What then are the limits to non-stop flight, and can we expect to see these records beaten in the future? Non-stop flights are common among migratory shorebirds (also known as waders) and often involve trans-oceanic crossings, with examples being American golden plovers (Pluvialis dominica) flying 4,000 km between Nova Scotia and South America [7], ruddy turnstones (Arenaria interpres) flying 4,000 km between the Pribilof Islands and Hawaii [8], and red knots (Calidris canutus) flying 4,800 km between the Wadden Sea and their breeding area on Taymyr [9]. The evidence that the flights are indeed non-stop has often been circumstantial up until now, being based on timing of departure and arrival at main staging sites and how long the journey might take given the amount of fuel accumulated before departure; it is only recently that satellite-based tags have become small enough to allow individual shorebirds to be directly tracked as they migrate [10]. This technique enabled Gill et al. [6] to make their recent observations, and there is more recent circumstantial evidence that sharp-tailed sandpipers (Calidris acuminata) make a similar non-stop flight [11] (Figure 2). Figure 2 Sharp-tailed sandpiper.

Predicting the effects of masking noise on communication distance in birds.

Anthropogenic noise (e.g., highway noise) that exceeds natural ambient sound levels potentially can mask important acoustic signals used by birds during communication. Signals degraded by masking can in turn adversely affect critical behaviors such as mate attraction, territorial defense, parent-offspring communication, predator avoidance, and prey detection. The amount of masking depends not only on the physical characteristics of the noise (intensity, frequency, temporal pattern, etc.) but also the auditory capacity of the species, the acoustic structure of their vocal signals, the proximity of the birds to the noise source and each other, and the sound attenuation properties of the habitat. Here we present a quantitative model for predicting effective communication distances between birds subject to different levels and types of anthropogenic noise. Cross-species analysis shows that communication distances are largely context/environment dependent and species specific. Extrapolation of noise impact distance estimates even within groups of similar species should be exercised with caution. This model should be useful in environmental impact analysis of anthropogenic noise on birds and other wildlife, particularly species of conservation concern.

Does intruder group size and orientation affect flight initiation distance in birds?

Wildlife managers use flight initiation distance (FID), the distance animals flee an approaching predator, to determine set back distances to minimize human impacts on wildlife. FID is typically estimated by a single person; this study examined the effects of intruder number and orientation on FID. Three different group size treatments (solitary person, two people side-by-side, two people one-behind-the-other) were applied to Pied Currawongs (Strepera graculina) and to Crimson Rosellas (Platycerus elegans). Rosellas flushed at significantly greater distances when approached by two people compared to a single person. This effect was not seen in currawongs. Intruder orientation did not influence the FID of either species. Results suggest that intruder number should be better integrated into estimates of set back distance to manage human visitation around sensitive species.

Exposure To Predators and Access To Food in Wintering White-Throated Sparrows Zonotrichia Albicollis

AbstractI studied a free-living population of white-throated sparrows (Zonotrichia albicollis) to determine which, among eleven behavioural, morphological and situational variables, were correlated with the distance from cover at which individuals fed (a presumed index of predation risk) and the amount of time they spent feeding at three observation sites. Time spent feeding was correlated only with dominance, an indication that dominant birds obtained greater access to high quality food. In contrast, an assortment of factors affected distance to cover. Individuals tended to feed far from cover if they were: (1) in large flocks, (2) males, (3) young and (4) subordinate. Distance to cover for the population as a whole increased during cold and cloudy conditions. The failure of dominance alone to determine a bird's distance to cover probably resulted in part from the confusion caused by dominant heterospecifics (e.g. cardinals, Cardinalis cardinalis) and from their apparent tendency to tolerate mainly small white-throated sparrows (which tended to be subordinate) feeding with them. Overall, this study indicates that while dominance clearly allows easy access to food, it is only one of several factors affecting exposure to predators.