共查询到20条相似文献，搜索用时 15 毫秒
1.
Capsule Within-pair comparisons substantially improve the accuracy of sexing from biometrics for two congeneric species of seabird with monomorphic plumage and soft-tissue colouration. Aims To examine the extent to which statistical limitations of sexing birds from biometrics using sample-level analysis could be overcome by sexing Common and Arctic Terns (Sterna hirundo and S. paradisaea) using measurements obtained from breeding pairs. Methods Incubating adults were caught at the nest using walk-in traps and wing, tarsus, head-plus-bill, tail length, tail fork, and body mass measured. Each bird was individually colour-ringed and dyed with picric acid, enabling subsequent sexing by behavioural observations of copulation and courtship feeding. Birds were sexed using biometrics and the proportion of birds sexed correctly this way at the sample level was compared with the accuracy achieved if, within a pair, the larger bird was classified as male. Results Head-plus-bill length was the single most accurate measurement for sexing individuals of both species, and correctly classified 72% of Arctic Terns and 73% of Common Terns. Combinations of measurements derived from discriminant analysis achieved slightly higher accuracy (73% and 78% respectively). Within-pair comparisons were more accurate than sample-level analysis for both single measurements and discriminant functions, and were able to sex 84% of Arctic Terns and 86% of Common Terns correctly. Conclusion Comparing birds within pairs improves accuracy and can eliminate the need to calculate cut points or discriminant functions from a sample of birds of known sex for each particular study. We strongly advocate such comparisons wherever possible to increase accuracy and simplify computational procedures for predicting sex, thus reducing associated sources of error. 相似文献
2.
ABSTRACT Defining the at‐sea foraging movements of seabirds is fundamental to understanding their ecology and can also be important in assessing the potential impact of marine developments such as offshore wind farms (OWFs). Surveys of predefined areas using aerial or boat‐based transect surveys may not allow adequate assessment of the relative importance of different areas to birds. Individual‐based satellite or radio‐telemetry can be effective in identifying foraging ranges and preferred areas, but may not be suitable for some species. We developed a method to determine the foraging movements of breeding terns (Sterna spp.) by visually tracking individuals using a rigid‐hulled inflatable boat (RHIB). Sandwich Terns (S. sandvicensis), Common Terns (S. hirundo), and Arctic Terns (S. paradisaea) were tracked from colonies in Norfolk and Anglesey, United Kingdom, from 2006 to 2008. The proportion of complete (from and to colony) trips varied from 29–60% among species, years, and colonies. Individual Sandwich Terns were tracked for periods up to 126 min over distances up to 72 km and as far as 54 km from the breeding colony, further than Arctic (up to 57 km and 29 km from the colony) and Common (to 29 km and <9 km from the colony) terns. Mean values were much smaller. Multivariate modeling of Sandwich Tern foraging trips indicated that flight speeds >50 km/hr coupled with greater distances from shore (>25 km) significantly reduced the likelihood of tracking a bird for an entire foraging trip. Use of different boats that differ in speed and performance may alleviate such issues. Visual tracking allowed us to collect data on foraging behavior, flight height, and prey capture rates, and also permitted comparisons between species. Our results indicate that visual tracking may be an effective means of determining the foraging movements and at‐sea behavior of a variety of short‐ranging, day‐active seabirds. 相似文献
3.
2009年4～7月,采用定点观察法和逐巢清点法,对陕西省红碱淖地区普通燕鸥(Sterna hirundo)和鸥嘴噪鸥(Gelochelidon nilotica)的繁殖生态进行了比较研究。结果表明,两者都是4月末迁至红碱淖,并于5月中旬进入繁殖期。普通燕鸥和鸥嘴噪鸥都选择在湖心岛上营巢,普通燕鸥巢址沿岛边缘四周呈线状分布,而鸥嘴噪鸥位于岛中央向外扩散呈块状分布。对食物调查发现,两者在食物资源利用上存在部分生态位分离。巢址分布格局差异性和食物资源利用生态位部分分离是两者能在同一领域共存的主要原因。对雏鸟的体重等形态参数进行Gompertz曲线方程拟合,结果表明,两种雏鸟生长状况的差异性从另一面也可以反应二者种间竞争压力的缓和。另外,从一定的角度分析了两者与遗鸥(Larus relictus)的伴生关系。 相似文献
4.
GUILLERMO BLANCO MARCELO BERTELLOTTI 《Biological journal of the Linnean Society. Linnean Society of London》2002,75(2):137-146
Selection for crypsis in varying environments has long been established as the main evolutionary force promoting the huge variation in avian egg coloration. In several avian species, variation in egg coloration exists, but available information available on the relative success of these different colour morphs against predation is scarce. We investigated the value of eggshell coloration against mammal and avian predators in the South American Tern, Sterna hirundinacea. We found evidence of a relationship between particular eggshell ground coloration and success against predation, in different tern colonies, where strong selection was caused by single avian and mammalian predator species. Survival to hatching of eggs with greenish ground coloration was greater than in eggs of the remaining colours when a mammalian carnivore was present. This implies that the human visual system does not accurately represent predator perception but that, viewed through the predator's eyes, the conspicuous greenish eggs are well concealed. The rate of artificial nest predation by visually searching gulls was higher for eggs more conspicuous to the human eye than for eggs more closely resembling the nest substrate. The evolution of polymorphisms in eggshell ground colour may have resulted from differences in the type of predator present, and differences in choice of breeding site varying in the background substrate. The nomadic breeding behaviour of terns may imply that females differing in the frequency of alleles expressing particular egg coloration, selected for in particular environments, may eventually gather in some colonies, thus producing the observed intracolony variation in egg coloration. We hypothesise that egg colour variation could be maintained in the population by shifting peaks of predation impact in the different locations where colonies form, e.g. islands without mammalian predators vs. mainland sites. 相似文献
5.
6.
Rebecca Croston Sarah H. Peterson C. Alex Hartman Mark P. Herzog Cliff L. Feldheim Michael L. Casazza Joshua T. Ackerman 《Ecology and evolution》2021,11(12):7292
Incubating birds must balance the needs of their developing embryos with their own physiological needs, and many birds accomplish this by taking periodic breaks from incubation. Mallard (Anas platyrhynchos) and gadwall (Mareca strepera) hens typically take incubation recesses in the early morning and late afternoon, but recesses can also take place at night. We examined nocturnal incubation recess behavior for mallard and gadwall hens nesting in Suisun Marsh, California, USA, using iButton temperature dataloggers and continuous video monitoring at nests. Fourteen percent of all detected incubation recesses (N = 13,708) were nocturnal and took place on 20% of nest‐days (N = 8,668). Video monitoring showed that hens covered their eggs with down feathers when they initiated a nocturnal recess themselves as they would a diurnal recess, but they left the eggs uncovered in 94% of the nocturnal recesses in which predators appeared at nests. Thus, determining whether or not eggs were left uncovered during a recess can provide strong indication whether the recess was initiated by the hen (eggs covered) or a predator (eggs uncovered). Because nest temperature decreased more rapidly when eggs were left uncovered versus covered, we were able to characterize eggs during nocturnal incubation recesses as covered or uncovered using nest temperature data. Overall, we predicted that 75% of nocturnal recesses were hen‐initiated recesses (eggs covered) whereas 25% of nocturnal recesses were predator‐initiated recesses (eggs uncovered). Of the predator‐initiated nocturnal recesses, 56% were accompanied by evidence of depredation at the nest during the subsequent nest monitoring visit. Hen‐initiated nocturnal recesses began later in the night (closer to morning) and were shorter than predator‐initiated nocturnal recesses. Our results indicate that nocturnal incubation recesses occur regularly (14% of all recesses) and, similar to diurnal recesses, most nocturnal recesses (75%) are initiated by the hen rather than an approaching predator. 相似文献
7.
K. Lesley Szostek Peter H. Becker Barbara C. Meyer Stefan R. Sudmann Heribert Zintl 《Ibis》2014,156(1):48-59
Density is known to be an important factor in population size regulation. Several mechanisms of density limitation have been identified in colonial birds. We studied competition in Common Terns Sterna hirundo to assess whether the factor limiting reproductive output was competition for nest‐sites, which is dependent on local nest density, or density‐dependent competition for food resources, which is dependent on overall colony size using the same foraging area. We found strong associations of both colony size and nest density with reproductive output in five colonies of Common Terns in three different habitats (one marine, two freshwater). Based on detailed long‐term datasets of six separate sub‐colonies of the Banter See colony that differed in nest density, we found that reproductive success was not related to nest density but to overall colony size, possibly a result of resource depletion and food competition. We also found carry‐over effects of colony size during rearing on post‐fledging return rate. These results have important implications for the conservation management plans aimed at recovering declining populations of Common Terns. 相似文献
8.
Predator odors such as urine and feces are known to elicit antipredator behaviors in prey including avoidance, fear, and curiosity. We measured how wild brown mouse lemurs (Microcebus rufus) responded to odors of mammalian, avian, and snake predators as well as nonpredator controls. The first experiment took place under controlled conditions in a laboratory where we recorded the occurrence of four behavioral categories (ignore, curiosity, alert, and fear) in response to a single odor. Subjects exhibited behavioral change significantly more often in response to the predator than to control stimuli, but did not distinguish between familiar and unfamiliar predators. Mammalian predator urine and feces were most likely to elicit behavioral change. The owl was the only predator to never elicit behavioral change, possibly because owls do not provide relevant odor cues. A second experiment employing live traps in the forest found that neither predator nor control odors affected the likelihood of capture. Due to their longevity, odors do not provide accurate information of spatial and temporal risk, and while mouse lemurs may have initially hesitated to enter a trap, in the absence of additional information about risk, they may have eventually ignored the stimuli. This study found that brown mouse lemurs are able to distinguish between predator and nonpredator odors, and that risk assessment may be affected by the experience, as well as predator and sensory stimulus quality. 相似文献
9.
Daniel H. Catlin Joy H. Felio James D. Fraser 《The Journal of wildlife management》2011,75(2):458-462
We studied the effect of great-horned owl (Bubo virginianus) removal on piping plover (Charadrius melodus) hatchling survival on Missouri River sandbars (2008–2009). Owl removal increased daily survival of piping plover chicks in 2008 (β = 2.03, 95% CI: 0.04–4.02), but this effect decreased with increasing age of the chick (β = −0.42, 95% CI: −0.81 to −0.03). Results for 2009 were similar in direction but not significant. Survival was higher in 2008 than in 2009, regardless of owl capture, indicating that even if owl capture consistently were effective at increasing survival, overall survival resulting from trapping may vary annually. Owl trapping was a successful means to raise chick survival on the Missouri River in ≥1 year and could be used at other sites experiencing depressed chick survival due to avian predators. © 2011 The Wildlife Society. 相似文献
10.
Anna Lena Burger Julian Fennessy Stephanie Fennessy Paul W. Dierkes 《Ecology and evolution》2020,10(6):2917-2927
This study presents the first findings on nocturnal behavior patterns of wild Angolan giraffe. We characterized their nocturnal behavior and analyzed the influence of ecological factors such as group size, season, and habitat use. Giraffe were observed using night vision systems and thermal imaging cameras on Okapuka Ranch, Namibia. A total of 77 giraffe were observed during 24 nights over two distinct periods—July–August 2016 (dry season) and February–March 2017 (wet season). Photoperiod had a marked influence on their activity and moving behavior. At dusk, giraffe reduced the time spent moving and increasingly lay down and slept at the onset of darkness. Body postures that likely correspond to rapid eye movement (REM) sleep posture (RSP) were observed 15.8 ± 18.3 min after giraffe sat down. Season had a significant effect with longer RSP phases during the dry season (dry: 155.2 ± 191.1 s, n = 79; wet: 85.8 ± 94.9 s, n = 73). Further analyses of the influence of social behavior patterns did not show an effect of group size on RSP lengths. When a group of giraffe spent time at a specific resting site, several individuals were alert (vigilant) while other group members sat down or took up RSP. Simultaneous RSP events within a group were rarely observed. Resting sites were characterized by single trees or sparse bushes on open areas allowing for good visibility in a relatively sheltered location. 相似文献
11.
Habitat selection is a complex process, that is affected by several factors, including habitat characteristics, environmental conditions, and both intra‐ and interspecific interactions. We analysed habitat preferences of two top avian predators, Peregrine Falcon Falco peregrinus, a medium‐sized diurnal raptor, and Eagle Owl Bubo bubo, a large nocturnal raptor. These two species are known to compete for preferred nest‐sites, and proximity to cliffs with Eagle Owls may reduce Peregrine breeding output through predation of young Falcons. We investigated the environmental factors affecting occurrence and coexistence of the two species and the potential role of habitat suitability in favouring co‐occurrence in 3519 km2 of the central pre‐Alps of Italy, where the two species breed on cliffs and sometimes co‐occur on the same cliff. Peregrines settled on long, steep and favourably orientated cliffs in woodland landscapes close to urban areas. Eagle Owls settled on topographically similar cliffs, but in lower rainfall areas compared with cliffs occupied by Peregrines and cliffs unoccupied by either species. Sites where the two species co‐occurred were characterized by more horizontally extended cliffs compared with sites of exclusive occurrence of each species. An analysis of relative habitat suitability revealed that sites where the two species co‐occurred had the highest predicted probability of occupancy for both species, suggesting that those sites should be regarded as high‐quality sites. Breeding productivity of Eagle Owls was negatively affected by the co‐occurrence of Peregrines, whereas the effect of Eagle Owl proximity on Peregrine productivity varied according to cliff suitability for the Peregrines. Habitat selection had fitness consequences for Eagle Owls because breeding productivity increased with cliff length. Environmental conditions, particularly climatic factors, could allow the widespread coexistence of these competing raptors at the landscape scale, whereas at the local scale co‐occurrence could take place only on larger cliffs. These were preferred sites for both species, presumably because breeding at such sites offsets the costs of settling close to the competitor species. 相似文献
12.
13.
José Ragusa-Netto 《Studies on Neotropical Fauna and Environment》2013,48(3):219-226
A nuclear or leader species is the one around which foraging activity is organized. In the campo-cerrado (Brazilian savannah) up to four bird species (Saltator atricollis, Cypsnagra hirundinacea, Mimus saturninus, and Neothraupis fasciata) may function as nuclear or leader species in mixed species flocks. The aim of this study was to assess the features shown by these nuclear species. I quantified parameters of sociality, communication and alertness of nuclear bird species in mixed flocks with different composition. Parameters related to sociality (mean intraspecific group size) and communication (frequency of contact calls) were not correlated with the leadership. On the other hand, the most alert species was in the front of a given mixed flock most of the time. The leader species spent more time in vigilance and gave most alarm calls due to approaching raptors earlier. The results of this study strongly suggest that the alertness of a species is the major character of nuclear bird species in mixed flocks of the campo-cerrado. 相似文献
14.
Shawn P. Haskell Warren B. Ballard Mark C. Wallace Mary H. Humphrey David A. Butler 《The Journal of wildlife management》2010,74(8):1686-1692
ABSTRACT Postpartum behavior of maternal deer may be specific to species of deer and predators. We captured sympatric white-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus eremicus) fawns from radiocollared adult females in 2004–2006 on rangelands of west central Texas, USA, where predators larger than bobcats (Lynx rufus) were absent. Our objective was to determine whether differences in postpartum antipredator behavior existed between deer species, and if so, examine efficacy of those strategies. We collected postpartum group cohesion data in 2004 and 2005 by using radiotelemetry and examined dead fawns for cause of mortality. During fawns' hider phase, <3 weeks postpartum, mule deer females kept fawns closer to themselves (95% CI = 39−66 m) and twins closer to each other (95% CI = 25–49 m) than did white-tailed deer females (95% CIs = 152–234 m and 163–255 m, respectively). After 30 days postpartum, familial group cohesion was similarly tight for both species. During hider phases from 2004 to 2006, predated carcasses of white-tailed deer fawns (11 of 11) were dismembered or consumed more than mule deer fawns (7 of 13, P = 0.016), which was one line of evidence for maternal defense by mule deer adults. During hider phases in 2004 and 2005, predation rate of mule deer fawns was lower than that for white-tailed deer fawns. In 2006, predation rate increased for mule deer but was similar for white-tailed deer fawns compared with previous years. The tight cohesion strategy of mule deer exhibited in 2004 and 2005 seemed successful at thwarting small predators. Without large predators, the loose cohesion strategy of white-tailed deer females was maladaptive. When meso-predators are abundant due to extermination of larger predators, predation on fawns could increase if a deer species has relatively fixed postpartum maternal antipredator behavior. 相似文献
15.
Abstract.— Incubation behavior is one component of reproductive effort and thus influences the evolution of life-history strategies. We examined the relative importance of body mass, frequency of mate feeding, food, nest predation, and ambient temperature to explain interspecific variation in incubation behavior (nest attentiveness, on- and off-bout durations, and nest trips per hour) using comparative analyses for North American passerines in which only females incubate. Body mass and frequency of mate feeding explained little variation in incubation behavior. We were also unable to detect any influence of food; diet and foraging strategy explained little interspecific variation in incubation behavior. However, the typical temperature encountered during reproduction explained significant variation in incubation behavior: Species breeding in colder environments take shorter bouts off the nest, which prevents eggs from cooling to temperatures below the physiological zero temperature. These species must compensate for shorter off-bouts by taking more of them (thus shorter on-bouts) to obtain needed energy for incubation. Nest predation also explains significant variation in incubation behavior among passerines: Species that endure high nest predation have evolved an incubation strategy (long on- and off-bouts) that minimizes activity that could attract predators. Nest substrate explained additional variation in incubation behavior (cavity-nesting birds have shorter on-bouts and make more frequent nest trips), presumably because nest predation and/or temperature varies among nest substrates. Thus, nest predation can influence reproductive effort in a way previously not demonstrated–by placing a constraint on parental activity at the nest. Incubating birds face an ecological cost associated with reproductive effort (predation of entire brood) that should be considered in future attempts to explain avian life-history evolution. 相似文献
16.
Monif AlRashidi 《Zoology in the Middle East.》2016,62(2):105-111
The breeding biology of the Kentish Plover Charadrius alexandrinus was studied in the Sabkhat Al-Fasl Lagoons of Saudi Arabia, where ground temperatures may ex- ceed 55°C in summer. Although halophytic bushes are abundant, this species seems to prefer nesting at exposed sites. Biparental brood care was common: the females were absent in only three out of 24 families. Kentish Plovers attended their nests more than 80% over the full day and more than 90% of the time during day-time, and the number of change-overs increased during the hottest parts of the day which could be due to the possibility that a single parent cannot protect the eggs and itself from overheating. 相似文献
17.
The productivity of the British Field Vole population is estimated to be between 677 000 and 982 000 voles per year, depending on the precise basis of the calculation. The total consumption of Field Voles by all the major predators, mammalian and avian, is estimated to be around 980 000, if the very uncertain consumption by Feral Cats is included. Two specialist vole predators (Weasel, Kestrel) and two generalist predators (Red Fox, Feral Cat) consume 85% of the total between them, the other 10 species share the rest between them. However important voles might be for owls, owl predation is unimportant to voles. The slight evidence for cyclicity in Field Vole populations in Britain might be explained by the overall take of voles by the predators, and by the rather generalized diet of even the vole specialists. 相似文献
18.
Sleeping cluster composition and distribution were studied in a semi-free-ranging population of 174 Barbary macaques (Macaca sylvanus) in Rocamadour/France. Over a period of 2 months 341 sleeping clusters comprising 754 animals were recorded as animals left the sleeping trees. To control for nocturnal activities five observation periods were conducted, each of which covered a complete night. Sleeping partners were selected from a particular set of individuals. From night to night there was considerable fluctuation among the individuals, which finally formed a sleeping cluster. Preferred size of sleeping clusters was two and three individuals per cluster. The majority of females spent the nights in body contact to infants or female juveniles; whereas males either slept alone or with older male juveniles. Adult males and females never shared a sleeping cluster. During the night the animals showed hardly any locomotive and vocal activity. Sleeping clusters remained stable until dissociation the next morning. © 1992 Wiley-Liss, Inc. 相似文献
19.
20.
Troy W. Grovenburg Christopher C. Swanson Christopher N. Jacques Robert W. Klaver Todd J. Brinkman Benjamin M. Burris Christopher S. Deperno Jonathan A. Jenks 《The Journal of wildlife management》2011,75(1):213-220
Understanding the influence of intrinsic (e.g., age, birth mass, and sex) and habitat factors on survival of neonate white-tailed deer improves understanding of population ecology. During 2002–2004, we captured and radiocollared 78 neonates in eastern South Dakota and southwestern Minnesota, of which 16 died before 1 September. Predation accounted for 80% of mortality; the remaining 20% was attributed to starvation. Canids (coyotes [Canis latrans], domestic dogs) accounted for 100% of predation on neonates. We used known fate analysis in Program MARK to estimate survival rates and investigate the influence of intrinsic and habitat variables on survival. We developed 2 a priori model sets, including intrinsic variables (model set 1) and habitat variables (model set 2; forested cover, wetlands, grasslands, and croplands). For model set 1, model {Sage-interval} had the lowest AICc (Akaike's information criterion for small sample size) value, indicating that age at mortality (3-stage age-interval: 0–2 weeks, 2–8 weeks, and >8 weeks) best explained survival. Model set 2 indicated that habitat variables did not further influence survival in the study area; β-estimates and 95% confidence intervals for habitat variables in competing models encompassed zero; thus, we excluded these models from consideration. Overall survival rate using model {Sage-interval} was 0.87 (95% CI = 0.83–0.91); 61% of mortalities occurred at 0–2 weeks of age, 26% at 2–8 weeks of age, and 13% at >8 weeks of age. Our results indicate that variables influencing survival may be area specific. Region-specific data are needed to determine influences of intrinsic and habitat variables on neonate survival before wildlife managers can determine which habitat management activities influence neonate populations. © 2011 The Wildlife Society 相似文献