Territorial Pairs Research Articles

The ecology of the habitats, nesting, and migration of the eastern population of the siberian crane (Grus leucogeranus Pallas, 1773)

The structure of the distribution range and population of the Siberian crane in its regular breeding area in the northeastern Yakutian tundra are described, as well as the migration terms, intensity, routes, and stopover sites. The territorial pairs (71.7–97.1% of the summer population), which in 2006 were represented by the birds at ages of 8 to 21 years (mainly 20 years, accounting for 45.4%), constantly stayed on an area of 7.3–16.5 km2 independently of their participation in breeding. The breeding success in this population varies from 4.3–8.7 to 65.0–83.3% and depends on the climatic conditions at the beginning of egg laying; these climatic conditions change rather unpredictably from year to year, as well as being seasonally unstable. This explains that fact that some generations in this population are particularly vulnerable to natural elimination factors because of their low numbers. Bird migration in Yakutia follows a narrow tunnel with the highest migratory intensity in the Middle Aldan Valley. In the fall, 30 to 50% of the entire population is visually recorded there.

Local–foreign dialect discrimination and responses to mixed-dialect duets in the North Island kōkako

Social discrimination based on geographic variation in territorial signals is taxonomically widespread—most studies have found stronger reactions to local than to foreign signals. In birds with male-only song, this discrimination is thought to result in social exclusion and has been suggested as a behavioral barrier to interpopulation genetic exchange. However, little information exists on duetting species in this context, and nothing is known of how “mixed-dialect” pairs are perceived, despite their confirmed occurrence. We addressed these deficiencies using a duetting, endangered Passerine, the kō kako (Callaeas wilsoni). We used reciprocal stereo playback experiments between 2 fragmented populations to present duets from local and foreign dialects (Experiment 1). Additionally, we assessed responses to mixed-dialect pairs by synthesizing duets, a novel technique, to determine which sex contributes the most salient duet components (Experiment 2). Territorial pairs vocally responded to local duets with less delay, and produced more song phrases with a lower diversity, than they did in response to playback of foreign duets. Pairs responded to mixed-dialect duets with equal overall strength regardless of the sex of the local component. Responses to mixed and pure local duets were qualitatively similar. From an evolutionary perspective, this suggests that mixed-dialect pairs can successfully defend territories without social penalties, improving the likelihood of cross-dialect gene flow. These findings have particular importance for conservation efforts like translocation, which often involve individuals from multiple, culturally distinct populations. Key wor ds: Callaeas wilsoni , dialect, discrimination, duet, endangered species, North Island kōkako. [Behav Ecol]

Individual identity, song repertoire and duet function in the Crimson-breasted Shrike (Laniarius atrococcineus)

Avian vocal duets are joint displays where paired birds produce temporally and structurally coordinated vocalisations. Duets show great variety in form that can reflect different functions, such as mate guarding, mutual recognition, pair bond maintenance or territory defence. By describing the structure of duets and singing behaviour, we can investigate whether these signals are based on cooperation or conflict and which functions they might have. Here we describe the singing behaviour and song repertoire of the Crimson-breasted Shrike in the Kalahari Desert, and assess four main hypotheses proposed for the function of duets. We found that Crimson-breasted Shrikes have a sex-specific repertoire, and the individuality of males, females and pairs is expressed acoustically. Differences in vocal strategies between the sexes indicate male mate guarding as one possible function. Temporal coordination is high and duetters follow strict codes, suggesting that duetting could be a cooperative endeavour in this species. The observed duetting behaviour is also consistent with the predictions for mutual recognition because each bird has its individual vocal characteristics that are consistent over time. Our results provide no support for the hypothesis that duets serve pair bond maintenance in this species as no partner-directed adjustment of temporal coordination took place.

Vocal behaviour of Barred Antshrikes, a Neotropical duetting suboscine bird

Despite the high biodiversity that characterizes the tropics, we know little about the behaviour of most tropical birds. Antbirds (Thamnophilidae) are a biodiverse family of more than 200 species found throughout Central and South America, yet their ecology and behaviour are poorly known. In this study, we provide the first detailed description of the vocalizations and vocal behaviour of Barred Antshrikes (Thamnophilus doliatus), a widespread Neotropical suboscine passerine. We studied 38 territorial pairs in a population in Costa Rica from 2008 to 2010, using field recordings and observations to quantify their vocalizations and vocal behaviour. Males and females produced similar songs consisting of rapidly repeated chuckling notes. Several aspects of their songs distinguish the sexes: male songs were longer in duration, contained more syllables, and were lower in pitch. Males had a higher song output than females, but within song bouts males and females sang at similar rates. Barred Antshrike song output varied daily, with the highest song output occurring at dawn. Song output also varied seasonally, with increased song output occurring during the breeding period. Males and females combined songs to create duets, overlapping the terminal portion of their mate’s song. Most duets were created by females responding to male songs (84 %), and the rest by males responding to female songs. The timing of duet responsiveness varied between the sexes; males responded more quickly to their partner’s song (1.6 s) than females (2.0 s). This detailed account of the vocalizations and vocal behaviour of a population of Barred Antshrikes creates a foundation for future comparative studies of antbirds. Our study highlights similarities and differences in the behavioural patterns of tropical birds and contributes to our understanding of the function of vocal duets and the vocal behaviour of antbirds.

Male Common Loons Signal Greater Aggressive Motivation By Lengthening Territorial Yodels

Abstract We examined two critical predictions of the hypothesis that male Common Loons (Gavia immer) communicate greater aggressive motivation by increasing the number of repeat syllables within their territorial yodels. We observed (from >3,500 hrs of field observations of 58 males) the probability that territorial interactions escalated from territorial flyovers by intruders to stereotyped ‘social gatherings’ to escalated fights between residents and intruders was positively correlated to the number of repeat syllables given by individually-banded males. Males yodeling during these escalated contests often assumed the upright ‘vulture’ posture rather than the usual ‘crouch’ posture, reflecting an escalated aggressive motivational state. Territorial pairs responded sooner and with more threat and alarm vocalizations to playback yodels that contained more repeat phrases. This reflected a greater willingness to attack by residents to perceived intrusions by males of higher aggressive motivational state. Ou...

Densities and dispersion of breeding Eurasian Hobbies Falco subbuteo in southeast England

Capsule Breeding Hobbies are more numerous in parts of southeast England than previously recognized, and in suitable habitat their breeding dispersion shows a regular pattern. Aims To establish the density and breeding dispersion pattern of a population of Hobbies in southeast England. Methods Surveys to locate every pair of Hobbies present were conducted in six study areas of between 48.0 and 201.2 km2 in three counties in southeast England during 2005–10. Results Each study area held between 7 and 21 pairs. Densities were higher than in previous studies conducted in Britain, at between 9.0 and 15.0 pairs per 100 km2. Mean densities per unit area of non-developed habitat were also consistently higher than expected, at between 10.1 and 17.3 pairs per 100 km2. The mean nearest known neighbour distances fell within the range 1.8–2.8 km. In all six study areas, pairs were regularly spaced. The majority (68.0%) of nesting and territorial pairs occupied sites in woodland. Conclusions Breeding Hobbies are considerably more numerous in parts of southeast England than previously recognized, and numbers appear to be continuing to increase. Accurate population estimates for Hobbies require species-specific fieldwork.

Monitoring of wolves in Scandinavia

The Scandinavian wolf population is jointly monitored by Norwegian and Swedish authorities. Monitoring is made annually. Wolves are classified in different categories. Family groups (>= 3 animals sharing a territory), territorial pairs, other stationary wolves, and vagrants. Also number of reproductions are determined each year, and has the highest priority as national management goals for the wolf population in both countries are expressed as number of reproducing units. Three methods are used in combination. Tracking on snow is the basic method. Around 100 field workers are employed full time or part time to find and follow tracks of wolves during the monitoring season Oct. 1 - Feb 28. The second method is DNA-analysis, mainly based on wolf scats collected during tracking. DNA-analysis help verifying reproductions, identifying newly established pairs, differentiating between neighboring territories and for identifying new immigrants from the Finnish/Russian population. The third method is radio telemetry. 10-20 wolves are equipped with GPS-collars each year, and used for determining of territory extents and differentiating between neighboring territories. All monitoring data are recorded in national databases, and compiled each year in an annual monitoring reports. Annual budget for large carnivore monitoring in the two countries combined in 2011 was approximately 5.8 million Euro, of which approximately 1.5 million was spent on wolves.

Territory occupancy by common loons in response to disturbance, habitat, and intraspecific relationships

AbstractStructure and distribution of animal territories are driven by a variety of environmental and demographic factors. A peninsular population of common loons (Gavia immer) nests on lakes in northwestern Montana, but does not occupy all apparently suitable breeding territories, suggesting unexplained limitations on population growth. To evaluate territorial dynamics of breeding loons in Montana, we created and tested occupancy models that evaluated the hypothesized effects of disturbance, habitat, and intraspecific relationships on territory occupancy by common loons in Montana from 2003 to 2007. Model‐averaged results indicated that the abundance of feeding lakes within 10 km (i.e., forage quality) and the number of territorial pairs within 10 km (i.e., density of loons) were equally supported and related to probabilities of occupancy. We found substantial support that the population was in a state of equilibrium, with the numbers of occupied territories stable in time, but not space. We also found that density of territorial pairs was related to the likelihood that an existing territory would be abandoned, but did not influence the establishment of new territories, suggesting the presence of territorial pairs could be a stronger indicator of territory quality to loons than physical lake characteristics. Our index of human disturbance was not well‐supported compared to other factors. Our results suggest management for stable or growing loon populations could be achieved using long‐term monitoring and protection of occupied territorial lakes and nearby feeding lakes, because these factors most influenced the probability of occupancy of surrounding lakes. © 2011 The Wildlife Society.

Settlement and Successful Breeding of Reintroduced Spanish Imperial EaglesAquila adalbertiin the Province of Cadiz (Spain)

Summary. A project to reintroduce the Spanish imperial eagle in the province of Cadiz (Andalusia, Spain) began in 2002. The aim was to restore the former breeding nucleus, to encourage subpopulation interconnection and to ensure the long-term persistence of the southern metapopulation of this endemic Iberian species. A population reinforcement programme also began in 2005 at a location in the Donana area (Andalusia, Spain) to improve the viability of this endangered subpopulation. Between 2002 and 2010, a total of 73 young Spanish imperial eagles were released at four locations by means of hacking. As a result, in 2010 a released male bred successfully with a non-reintroduced female and two young were reared. This was the first successful breeding event recorded in Cadiz province since 1960. An additional territorial pair also settled in the release area in 2010 and four more translocated individuals have made breeding attempts within nearby breeding subpopulations since 2006. The settlement and breeding ...

Duet Function in the Yellow‐Naped Amazon, Amazona auropalliata: Evidence From Playbacks of Duets and Solos

The question of why animals participate in duets is an intriguing one, as many such displays appear to be more costly to produce than individual signals. Mated pairs of yellow-naped amazons, Amazona auropalliata, give duets on their nesting territories. We investigated the function of those duets with a playback experiment. We tested two hypotheses for the function of those duets: the joint territory defense hypothesis and the mate-guarding hypothesis, by presenting territorial pairs with three types of playback treatments: duets, male solos, and female solos. The joint territory defense hypothesis suggests that individuals engage in duets because they appear more threatening than solos and are thus more effective for the establishment, maintenance and/or defense of territories. It predicts that pairs will be coordinated in their response (pair members approach speakers and vocalize together) and will either respond more strongly (more calls and/or more movement) to duet treatments than to solo treatments, or respond equally to all treatments. Alternatively, the mate-guarding hypothesis suggests that individuals participate in duets because they allow them to acoustically guard their mate, and predicts uncoordinated responses by pairs, with weak responses to duet treatments and stronger responses by individuals to solos produced by the same sex. Yellow-naped amazon pairs responded to all treatments in an equivalently aggressive and coordinated manner by rapidly approaching speakers and vocalizing more. These responses generally support the joint territory defense hypothesis and further suggest that all intruders are viewed as a threat by resident pairs.

Long-term monitoring of an insular population of Barbary Falcon Falco peregrinus pelegrinoides

Territory spacing and breeding rates of an insular population (north-western Tenerife, Canary Islands) of Barbary Falcon Falco peregrinus pelegrinoides was studied from 1993 to 2008. The population increased constantly since the outset, from two pairs in 1993 to 12 in 2008. Mean density was 5.48 pairs per 100 km2 and mean nearest neighbour distance was 3 119 m. The regularity of the spatial distribution pattern of the nests, observed in most years, may be maintained in the future despite the expectation that new pairs may occupy still-vacant territories. Considering the 79 breeding attempts analysed, the mean number of fledged young per territorial pair was 1.92, per laying pair was 2.0 (n = 76), and per successful pair was 2.24 (n = 68). No significant variations were observed between the annual mean number of fledged young per laying pair, nor between the number of fledged young of pairs according to density in a 5 km radius. All fledglings (brood size one to four) left the nest in the month of May. In order to avoid affecting breeding success, sporting activities practised in the breeding areas must be correctly managed by the appropriate authorities.

Aggressive responses to playback of solos and duets in a Neotropical antbird

Duetting behaviour is a unique form of animal communication that occurs in many diverse taxa in the animal kingdom. Hypotheses for the function of duets can be grouped into two broad categories to explain why individuals coordinate with their partner’s songs to create duets: (1) duets are cooperative displays where pair members have a shared goal, such as joint resource defence, and (2) duets are conflicting displays where pair members have different goals, such as guarding against divorce or extrapair copulations. To distinguish between cooperative versus conflicting functions of vocal duets, we conducted a playback experiment to 40 breeding pairs of barred antshrikes, Thamnophilus doliatus . We broadcast five playback treatments to territorial pairs of birds: solos of males and females, duets created by males responding to female songs and by females responding to male songs, and a heterospecific control. We categorized subjects’ behaviour in terms of vocal and physical responses. Male vocal and physical responses were significantly higher towards conspecific stimuli than towards heterospecific stimuli. Males tended to show more vocal responsiveness towards duet stimuli, although this tendency was not significant. We observed a similar pattern for female vocal responses. However, for physical responses, females showed significantly more intense responses towards female solo stimuli than towards any other conspecific treatment, suggesting that female antshrikes perceive rival females as an especially intense threat. Our results provide some support for a joint resource defence function for duetting in this species, while the high intrasexual aggression observed between females may indicate a form of mate guarding.

Ecological selection and sexual dimorphism in the sooty oystercatcher, Haematopus fuliginosus

AbstractMale and female sooty oystercatchers (subspecies Haematopus fuliginosus fuliginosus; Haematopodidae) have an average difference in bill length of 19%. We studied the relationship between this sexual dimorphism and foraging ecology at coastal sites in southern New South Wales, Australia. Intersexual foraging divergence was most striking in diet, with seven prey classes eaten exclusively by one sex (male: 4, female: 3), and all shared prey classes eaten in different proportions. Intersexual diet partitioning was also observed in energetic rewards gained from foraging, with females gaining highest energetic benefits from eating ascidians and males from eating limpets. Furthermore, within the most commonly consumed prey item, limpets, females gained higher energetic benefit from eating smaller sizes while males gained greater rewards from the largest limpet sizes. Intersexual divergence was also observed in several aspects of foraging behaviour. Finally, there was a significant effect of tidal cycles upon intersexual niche partitioning in this species; the degree of diet divergence varied between tide conditions and females had a consistently more efficient dietary intake on neap tides than males. Diet divergence in the sooty oystercatcher is greater than previously observed in any oystercatcher, and is correlated with the largest sexual bill dimorphism recorded in this family. It is argued that intersexual competition between territorial pairs is operating to diverge male and female bill morphology.

Barred owl occupancy surveys within the range of the northern spotted owl

AbstractThe range expansion by barred owls (Strix varia) into western North America has raised considerable concern regarding their potential effects on declining northern spotted owl (Strix occidentalis caurina) populations, yet most information on the occurrence of barred owls in the region is limited to incidental detections during surveys for spotted owls. To address this shortcoming we investigated response behavior, detection probabilities, and landscape occupancy patterns of barred owls in western Oregon, USA, during conspecific versus spotted owl call‐broadcast surveys. Subtle differences in barred owl response behavior to conspecific versus spotted owl vocalizations combined with minor procedural differences between species‐specific survey protocols led to a sizeable difference in estimated detection probabilities during conspecific (0.66, 95% CI = 0.61–0.71) versus spotted owl (0.48, 95% CI = 0.39–0.56) surveys. We identified 61 territorial pairs of barred owls during repeated surveys of a multi‐ownership study area with the probability of occupancy being highest in the structurally diverse mixture of mature and old forests that occurred almost entirely on public lands. Our findings suggest that research and management strategies to address potential competitive interactions between spotted owls and barred owls will require carefully designed, species‐specific survey methods that account for erratic response behaviors and imperfect detection of both species. Our sampling methods can be used by forest managers to determine the occurrence and distribution of barred owls with high confidence. © 2011 The Wildlife Society.

Isolation and Decline of A Population of the Orange-Breasted Falcon

Abstract. Probably always rare and local because of its ecology and specialized habitat, the small, isolated population of the Orange-breasted Falcon (Falco deiroleucus) in Belize and Guatemala, likely numbering fewer than 40 territorial pairs, appears to be in steep decline in Belize. Territory occupancy (n = 12 eyries) in the population we studied in Belize declined from 83% (1992 to 1997) to 54% (2003 to 2009), and occupancy in 2009 was only half the mean in the prior decade. Mean annual production of fledglings per territorial pair declined 35% from 0.77 to 0.50. Mean annual population productivity, which measures the combined effect of occupancy and fecundity, declined 57% from 0.90 to 0.38. In contrast, neither occupancy nor fledging success in Guatemala (n = 7 eyries) declined over the same time period. Historical records and recent surveys suggest that the Orange-breasted Falcon has been extirpated from much of Central America and southern Mexico and that its range is contracting in South America,...

Recovery dynamics and viability of the white-tailed eagle (Haliaeetus albicilla) in Germany

Understanding the effect of protection measures on recovery of endangered populations is crucial for assessing the efficiency of management plans. Following the ban of DDT, PCB and other detrimental chemicals in the 1970s, the German white-tailed eagle population recovered rapidly. Using nest monitoring data, dead recovery data and population dynamics models, we examined both short and long-term viabilities of the population. Between 1991 and 2005 the proportion of breeding pairs with an active nest among territorial pairs was α = 0.88 ± 0.007. Annual breeding success was γ = 0.62 ± 0.014. Mean fledged brood size was b = 1.50 ± 0.010 fledged/successful breeding pair. The analysis of dead recovery data of 1,273 individuals ringed as nestling between 1991 and 2006 allowed survival rates to be estimated. We needed to distinguish between “young” (5 years old) and “old” (older than 5 years) adults. Furthermore the annual survival rate was higher for juvenile and immature birds (0.921 ± 0.024) than for adults (s“young” = 0.760 ± 0.097 and s“old” = 0.875 ± 0.079), a pattern presumably explained by territorial fights. Finally, an age structured model was used to examine the joint effect of population regulation, environmental and demographic stochasticities. All results indicated that only pessimistic scenarios could lead to substantial extinction probabilities within 100 years. We conclude that management measures were successful in removing the main extinction factors of the population and that future conservation efforts need to focus on the remaining ultimate extinction causes.

Factors influencing the breeding performance of the Augur Buzzard Buteo augur in southern Lake Naivasha, Rift Valley, Kenya

The breeding performance of the Augur Buzzard Buteo augur in 1995–1998 was compared between three different areas south of Lake Naivasha, Kenya. These were: (1) a national park (Hell's Gate), (2) an undisturbed Acacia woodland-pasture (Mundui) and (3) an intensively farmed horticultural area (Sulmac-Oserian). Augur Buzzards in Mundui had the most optimal nesting habitat, produced the most fledglings (1.6 chicks per year), enjoyed an abundant food supply as their land was not heavily grazed, and suffered the least persecution. In contrast, Augur Buzzards in Hell's Gate produced the fewest fledglings (0.5 chicks per year). Their food supply was not abundant and their nests were confined to cliffs and short shrubs making them vulnerable to predation. Augur Buzzards in Sulmac-Oserian performed intermediately, producing 0.8 chicks per year and suffering the highest adult mortalities (12%) from human persecution. Height of grass in fields within a pair's territory was the most important variable in predicting whether Augur Buzzards attempted to breed or not. Mean annual adult mortality was lowest at Mundui (4.8%) and highest at Sulmac-Oserian (12%). Adult mortality and the success of previous breeding attempts were the most important predictors in determining breeding performance.

Rich Pickings Near Large Communal Roosts Favor ‘Gang’ Foraging by Juvenile Common Ravens, Corvus corax

Ravens (Corvus corax) feed primarily on rich but ephemeral carcasses of large animals, which are usually defended by territorial pairs of adults. Non-breeding juveniles forage socially and aggregate in communal winter roosts, and these appear to function as ‘information centers’ regarding the location of the rare food bonanzas: individuals search independently of one another and pool their effort by recruiting each other at roosts. However, at a large raven roost in Newborough on Anglesey, North Wales, some juveniles have been observed recently to forage in ‘gangs’ and to roost separately from other birds. Here we adapt a general model of juvenile common raven foraging behavior where, in addition to the typical co-operative foraging strategy, such gang foraging behavior could be evolutionarily stable near winter raven roosts. We refocus the model on the conditions under which this newly documented, yet theoretically anticipated, gang-based foraging has been observed. In the process, we show formally how the trade off between search efficiency and social opportunity can account for the existence of the alternative social foraging tactics that have been observed in this species. This work serves to highlight a number of fruitful avenues for future research, both from a theoretical and empirical perspective.

Nest-site Attendance of the Resident White-tailed Sea Eagle (Haliaeetus albicilla) Outside the Breeding Season

The territorial pairs of White-tailed Sea Eagle are mainly sedentary and highly faithful to breeding territories and nest-sites. Due to a dramatic population decrease, many recent studies deal with the population status and habitat requirements of the species, but contemporary data on the nest-site attendance activity of the recovered population outside the breeding season are scarce. In the present study, we analysed the bonds of resident adult Sea Eagles with their nest-sites outside the breeding season (20 September – 20 February). We found that Sea Eagles actively attend their nest-sites during the non-breeding season, however, nest-site attendance varied between months, but not between years. Besides, almost half of the checked pairs repaired old or built new nests long before incubation, during September–December. We discuss the obtained results in the light of nest-site protection from forestry-related disturbance and propose to extend the protection of Sea Eagle nest-sites from above mentioned dis...

Polybrominated Diphenyl Ethers in Peregrine Falcon (Falco peregrinus) Eggs from the Northeastern U.S.

A total of 114 peregrine falcon eggs from nests in Connecticut, Massachusetts, Maine, New Hampshire, Rhode Island, and Vermont were analyzed for polybrominanted diphenyl ethers (PBDEs). Eggs were collected from 1996 to 2006, excluding 1997 and 1998. Total PBDE concentrations ranged from 74.5 to 6610 ng/g wet weight, with a median of 440. These levels were generally higher than those observed in European peregrine eggs, but comparable to those in North American seabird eggs. Congener patterns differed from such seabirds and were dominated by BDE-153, followed by BDE-99, -183, -209, -197, -207, -154, -100, and -196; with lesser contributions from BDE-47, -208, -203, -201, -206, -202, -138, and -119. Urban and rural falcon eggs contained similar total PBDE concentrations but different congener profiles. Urban eggs exhibited higher BDE-209 concentrations and greater percentages of other highly brominated congeners. BDE-209 was detectable in all eggs, with concentrations ranging from 1.4 to 420 ng/g wet weight Five octa- and three nona-brominated congeners were also frequently detected, some likely derived from the biodegradation of BDE-209. Temporal analyses indicated no significant changes in concentrations of total PBDEs, or most individual congeners, during the study period. An exception was BDE-209. It exhibited a significant increase, with a doubling time of 5 years. Current PBDE burdens may be insufficient to cause noticeable adverse effects at the population level, as the number of territorial pairs increased in the past decade. However, the high BDE-209 concentrations, short doubling time, and likely biodegradation observed in peregrine eggs from the northeastern U.S. may supportthe need for additional deca-BDE regulations.