Flamingo breeding: The role of group displays

Group displays in flamingos have been presumed to play a role in stimulating synchronous nesting and in facilitating pair formation. This study compares the group displays and breeding success of a captive flock of Caribbean flamingos (Phoenicopterus ruber ruber) at the National Zoological Park between 2 years: the frequency and synchrony of group displays were measured for a flock of 17 in 1988 and then again in 1989 after flock size was increased to 21. In 1989 the rate of occurrence of display activity increased 48%, the synchrony of group displays increased 100%, the frequency of mounts and copulations almost doubled, and for the first time in the flock's history two fertile eggs were produced. The use of sprinklers to simulate rain had no effect on the group displays. The amount of naturally occurring rainfall in 1989 was almost twice that in 1988. The increased frequency and synchrony of group displays could be attributed to increased flock size, change in sex ratio, addition of strange individuals, or increased rainfall. This study, however, provides evidence for a relationship between behavioral stimulation from group displays and components of breeding success in flamingos.     

Low Foraging Success of Semipalmated Sandpipers at the Edges of Groups

Variation in foraging success in relation to spatial position in a group is little known in species that feed on mobile prey that can hide or flee upon disturbance by foragers. I examined the foraging success of individuals located either at the edge or at the centre of flocks of semipalmated sandpipers (Calidris pusilla) feeding on a burrowing amphipod (Corophium volutator) during migration stopover in the Bay of Fundy, Canada. The rates of pecking, prey capture and success were lower for individuals foraging at the edge than at the centre of flocks. Edge birds spent more time running and more time flying than centre birds. Edge birds moved away from the centre of the flock and made frequent short flights towards the centre. In contrast, centre birds rarely moved in a specific direction and flew mostly to relocate elsewhere with the whole flock. Sandpiper flocks foraged over a large area in a relatively short amount of time. In addition, amphipod density is high in this habitat. It thus appears unlikely that prey depletion or low food availability at the edges of groups could explain the spatial variation in foraging success. Low foraging success at the edges of flocks thus arose mainly because of time costs related to flock expansion and retraction. The effect of mutual interference among foragers and of predation risk by falcons is discussed with respect to flock expansion and retraction.     

Flock size and breeding success in flamingos

Using data on flocks of flamingos in Britain and Ireland, the relationship between flock size and breeding in captive flamingos was examined. Breeding flamingo flocks were significantly larger than nonbreeding flocks and larger flocks bred more frequently than smaller flocks. All Chilean flocks containing more than 40 birds have bred successfully; however, one flock of only 4 Chilean Flamingos has reared at least one chick. All Caribbean flocks over 20 birds have successfully reared a chick, yet the smallest flock to rear a chick was one of 14 birds. © 1992 Wiley-Liss Inc.     

婺源靛冠噪鹛生物学初探

靛冠噪鹛(Garrulax courtoisi),由原黄喉噪鹛(Garrulax galbanus)[复又被]剥离出来的一独立鸟种并由此而为中国南方之特有种,具两个地理上相互分离/分立的亚种,其指名亚种于中国东南、亚种simaoensis于中国西南;因其对繁殖生境之狭选性且群体数量之稀缺而被列为极危物种(CR)。十余年来野外调查结果表明,其指名亚种于繁殖季节几乎仅见于江西婺源,营巢于低地村落乡镇的林木间,为典型合作繁殖鸟种。统计结果显示,在婺源靛冠噪鹛各繁殖群体中,其每年的营巢数量从未超过该群体中个体数的1/3,接近1/3已是很好年景;若首批卵和/或雏鸟遭天敌捕杀,二次所筑之巢的数目则充其量不及该群体中个体数的1/5,且二次筑巢通常在首批卵和/或雏鸟遭捕杀后月余方才开始;野外未见婺源靛冠噪鹛在一年之内有第三次筑巢的现象。若以成鸟引领当年幼鸟离开其繁殖地即视其繁殖期成功结束,则从未记录到当年幼鸟的数量有达到该繁殖群成鸟数量1/4的例子,能够接近或达到1/5已属上乘;作为另一方面,婺源靛冠噪鹛的某个或某几个繁殖群由于巢卵遭捕食而在个别年份中无幼鸟问世却并不罕见。目前已能确定婺源靛冠噪鹛有9个繁殖群体,个体总量逾300只,且在过去的5年中其数量略呈增长趋势。另外,尽管10余年来野外找寻simaoensis亚种的努力从未间断,但无论在已知原产地并周边地带却一直未能[再]发现该亚种。     

Selection for synchronous breeding in the European starling

Colonial birds often demonstrate considerable breeding synchrony. In southern Sweden the semi-colonial European starling initiated the vast majority of clutches within one week. Laying dates were positively skewed so that many birds initiated clutches at similar dates early in the season. Breeding was further synchronised by a particularly strong clutch-size reduction equivalent to one third of an egg per day during the first part of the breeding season. The decline in clutch size with season also held true for separate age-classes of females, for individual females laying at different times at different years and for individual females laying at different times the same year. Trends in breeding success during nestling rearing were unlikely to explain the high degree of breeding synchrony or the seasonal decline in clutch size; nestling survival and growth were weakly related or unrelated to reproductive timing. In contrast recruitment success of fledged offspring declined sharply with season. Even within the synchronous laying period, defined as clutches initiated during the first week each year, local recruitment success declined. It is suggested that the early seasonal decline is caused by selection for synchronous fledging permitting the immediate formation of flocks after fledging, whereas the late seasonal trends may be caused by either population differences in female quality or deteriorating conditions for raising young.     

Effects of male courtship and gonadal steroids on pair formation, egg-laying, and serum LH in Canvasback ducks (Aythya valisineria)

The effects of social stimuli on the reproductive physiology of female birds have been widely studied. This study examined the endocrine and behavioural responses of female Canvasbacks ( Aythya valisineria ) to changes in the behavioural and endocrine states of the male, as signalled by his courtship displays. Male Canvasbacks exposed to female conspecifics exhibited a variety of courtship displays which increased significantly with testosterone administration. However, the testosterone-increased courtship displays of males did not increase female receptivity or serum LH, or stimulate reproductive development or egg-laying in unpaired females placed with them. Females confined in cubicles within a pen that held breeding pairs and a free-swimming flock had higher serum LH levels and laid more eggs than did females in cubicles in another pen without breeding pairs or a free-swimming flock. This suggests that social factors, such as vocalizations from a flock and breeding pairs, may increase serum LH and egg-laying in unpaired females. Oestradiol implants in female Canvasbacks did not elevate receptivity to courting drakes, nor did they stimulate pair formation, nesting activity, or egg-laying behaviour. Testosterone implants in drakes and oestradiol implants in females decreased serum LH in each group. These results show that increasing the amount of courtship is not adequate to stimulate pairing behaviour or increases in reproductive hormones. Thus, our results suggest that female receptivity to male courtship may be a key determinant of pair formation and consequent synchronization of the behaviour patterns between members of a pair of wild birds. Our results may further suggest a dissociation between effects of courtship and pair formation in wild Canvasbacks.     

Familiarity Breeds Tolerance: the Development of Social Stability in Flocking Siskins (Carduelis spinus)

Behavioural integration associated with the fusion of two flocks is analyzed in captive siskins (Carduelis spinus) by quantifying changes in social behaviour with time since joining. In general there was an increase in the incidence of tolerant behaviour, supplanting attacks and hopping withdrawals with time since fusion of the flocks. However, the number of displays and flights showed the opposite, negative, trend. Taking dominance status into account, the greatest change in behaviour with time since joining is an increase in tolerance by dominants of new flock companions. Factorial analysis of correspondences was used to study how different birds changed their behaviour with time since joining a flock. This analysis showed that the introduction of new birds did not disrupt relationships with familiar birds, and that residents are dominant in interactions with the incoming new flock companions. The analysis also demonstrated that relationships within the new flock had stabilized 20 days after the flocks had joined. The characteristics of the socially integrated group of siskins are quite similar to those described by Rohwer & Ewald (1981) in their shepherds hypothesis: dominants tolerate their subordinates feeding in close proximity, offering them a profitable feeding area, but also supplant them to obtain food; both dominants and subordinates benefit from being in a flock. As a consequence, constant changes of membership in flocks is costly not only because birds lose dominance status, but also the advantages of clear dominant and subordinate roles.     

Flock size and habitat-dependent food and energy intake of foraging Goldfinches

Summary During the breeding season Goldfinches (Carduelis carduelis L.) feed on milky ripe seeds of about 20 food plants. Individual Goldfinches joining a flock reduce the time spent vigilant with increasing flock size. Therefore birds feeding in flocks get an increased intake of kernels per time unit. This was measured for five different food plants (Dactylis glomerata (Gramineae), Knautia arvensis (Dipsacaceae), Senecio vulgaris, Taraxacum officinale, Tragopogon pratensis (Compositae)). In large-sized flocks, birds fed up to 2.3 times more kernels, than when feeding solitarily. In addition, visibility in the vegetation leads to a further increase of kernel intake. Thus feeding under good conditions as in recently mown areas, can raise kernel intake to the seven fold per time unit as compared to solitary feeding. The maximum ingestion rate of kernels was 98 per min which implies a head up-and-down movement every 0.6 s. The calculated energy intake of birds per time unit is lowest in Senecio and highest in Tragopogon. Thus the birds, when feeding on Tragopogon in larger flocks, can gain an energy intake 16 times higher than that reached when feeding on Senecio, despite of a higher kernel intake rate. The energy intake individual Goldfinches gain at the particular plant species is markedly increased with flock sizes up to eight birds, with larger flocks the intake increases only slightly.     

Role of mixed‐species flocks in the use of adjacent savannas by forest birds in the central Cerrado,Brazil

Abstract: We examined the role of mixed‐species flocks for forest birds during their breeding and non‐breeding seasons in the use of savannas adjacent to forests in central Cerrado, Brazil. Transect surveys (n = 64) were conducted in eight savanna patches. Distances of birds from forests were estimated. Recorded birds were classified as members or not of mixed‐species flocks. About half of the bird species recorded in savannas were found in at least one mixed‐species flock. As distance from the forest increased, the number of species in mixed‐species flocks tended not to vary, while the number of species foraging alone or in mono‐specific groups decreased. Thus, for some forest species, participation in mixed‐species flocks allowed a greater use of more distant savannas. This tendency of being in mixed‐species flocks at greater distances from forests also can be interpreted as a reluctance to forage alone or in mono‐specific groups due to higher predation risk in less protective vegetation distant from cover. There was strong seasonal variation in the participation of bird species in mixed‐species flocks. There were significantly more species in mixed‐species flocks than out of these associations in the non‐breeding season, while differences in the breeding season were not significant. These patterns occurred, in part because mixed‐species flocks tended to be more frequent, to have more species and to forage at greater distances from forests during the early non‐breeding season than in other periods. This study suggests that the formation of mixed‐species flocks plays an important role in promoting the use of adjacent savannas by forest birds at forest/savanna boundaries in Cerrado. It also pointed out a novel advantage gained by birds with participation in mixed‐species flocks – greater use of adjacent vegetation patches.     

Testosterone and its effects on courtship in golden-collared manakins (Manacus vitellinus): seasonal, sex, and age differences

Male golden-collared manakins gather on leks and perform an acrobatic display to attract females. In temperate breeding species, testosterone (T) activation of courtship displays has been well studied. Few studies have examined T activation of displays in tropical species; even fewer have explored the activational role of T in elaborate courtship displays such as in the manakin. In some tropical species, including manakins, territorial aggression or song behavior are uncoupled from T. We have previously shown that T activates display behavior in manakin males when endogenous T levels are low in the non-courtship season. To understand how T functions in breeding birds, we examined T levels in a large group of manakins sampled during the courtship and non-courtship season. In addition, during the courtship season, we gave T implants to adult males, juvenile males, and females. We found that T levels were low during the non-courtship season and comparatively higher on average during the courtship season. However, T levels were low in many adult males during the courtship season, especially when compared to temperate breeding species. Regardless of initial endogenous T levels during the courtship season, T implants did not increase the display frequency of adult males. T-treated females and juvenile males did display under similar conditions. Our data suggest that the effects of T on manakin display vary with season, sex, and age and that high T is not necessary for display.     

Environmental Conditions during Breeding Modify the Strength of Mass-Dependent Carry-Over Effects in a Migratory Bird

In many animals, processes occurring in one season carry over to influence reproductive success and survival in future seasons. The strength of such carry-over effects is unlikely to be uniform across years, yet our understanding of the processes that are capable of modifying their strength remains limited. Here we show that female light-bellied Brent geese with higher body mass prior to spring migration successfully reared more offspring during breeding, but only in years where environmental conditions during breeding were favourable. In years of bad weather during breeding, all birds suffered reduced reproductive output irrespective of pre-migration mass. Our results suggest that the magnitude of reproductive benefits gained by maximising body stores to fuel breeding fluctuates markedly among years in concert with conditions during the breeding season, as does the degree to which carry-over effects are capable of driving variance in reproductive success among individuals. Therefore while carry-over effects have considerable power to drive fitness asymmetries among individuals, our ability to interpret these effects in terms of their implications for population dynamics is dependent on knowledge of fitness determinants occurring in subsequent seasons.      

云南省纳帕海自然保护区越冬黑颈鹤的集群特征

2004年10月-2005年5月,在云南纳帕海自然保护区采用定点扫描法对越冬黑颈鹤(Grus nigricollis)的集群类犁和集群大小进行了观察.结果表明黑颈鹤夜间集群夜栖,形成较大的夜栖群,平均群体大小为67.9只(16-157,n=17):按照有无灰鹤加入,又将其分为同种集群和混种集群两种类型,其中同种集群的黑颈鹤数量占整个越冬种群的65.3%.在白昼,黑颈鹤以家庭鹤、集群鹤及特殊群体3种类型活动,家庭鹤和集群鹤的平均大小分别为2.7只(2-4,n=145)和16.1只(3-65,n=1017).黑颈鹤的集群大小并不稳定,在日内和月份间均有明显变化(P=0.000＜0.05).存越冬期,最大集群形成于12月,其次为11月和1月;在日内,早上8时集群最大,随后减小并保持相对稳定,18时黑颈鹤开始向夜栖地靠拢,使得集群再次开始增大.随后观察中还发现,黑颈鹤的家庭解体过程开始于3月底,当幼鹤被成鹤驱逐离群后,逐渐加入集群鹤活动,从而使得家庭鹤和集群鹤的大小和组成发生改变.黑颈鹤的集群大小和组成受自身状况、种内关系、天气、食物等多种因素的共同影响,随时间和季节变动而发生变化,是对自身、种群和环境条件变化的综合反映.     

Breeding behavior in a flock of Chilean flamingos (Phoenicopterus chilensis) at Dublin zoo

The breeding behavior of a flock of Chilean flamingos was observed over a 3‐month period during the peak of breeding activity. This species’ habitat is becoming increasingly vulnerable, and concern has been raised over a decline in wild stocks numbers in the past two decades. Breeding programs in zoos have been established, but with limited success because little is known about the precise criteria and conditions required for breeding these animals. This study was undertaken to gain insight into the breeding behavior of captive Chilean flamingos. A catalogue of mating rituals, nest acquisition and defense, and egg incubation behavior was obtained. The results suggest that new additions to the colony may trigger breeding in the subsequent year and that rainfall has little effect on captive reproductive success. Individually identifiable flamingos were followed throughout the breeding season and detailed quantitative data on their nesting, copulation, and social interactions were obtained. Zoo Biol 19:227–237, 2000. © 2000 Wiley‐Liss, Inc.     

Effects of population growth on Crested Tit Parus cristatus post-fledging settlement

From 1987 to 1993, the winter density of Crested Tits Parus cristatus in north Belgium increased 2.76 times. The increase was the result of high annual survival rates of both adult and first-year birds despite a low reproductive success (number of fledglings per female) due to high predation of nestlings. A fc-factor analysis assuming intermediate costs of post-fledging dispersal and settlement gave the best fit. First-year birds had two options when trying to settle in a prospective breeding territory: (1) establish a new territory during August or early September and defend it against neighbouring flocks during winter or immigrants in early spring or both, or (2) overwinter as a subordinate in a mixed-age flock and pair with a widowed adult or replace a territory owner in early spring ("hopeful dominant stategy"). Settlement strategies varied with density; at low density, only the hopeful dominant strategy was observed, whereas at higher density, both strategies occurred.     

卧龙自然保护区血雉的社群组织

１９９４年１１月至１９９５年９月在四川卧龙自然保护区五一棚地区,采用无线电追踪技术并结合野外观察,对血雉的社群组织进行了研究。血雉冬季集群活动,相邻群体相遇,有驱逐行为发生。分群配对时,雌鸟长距离迁移。血雉为单配偶制,配偶关系联结紧密,可维持整个繁殖季节。孵卵由雌鸟承担,取食时由雄鸟相伴,雌雄鸟共同育雏。繁殖季节不参加繁殖的亚成体雄鸟、参加繁殖的成体雄鸟或配偶对往往也有集群活动的倾向。在繁殖季节,     

Roosting of Yellow-naped Parrots in Costa Rica: estimating the size and recruitment of threatened populations

ABSTRACT.   Many parrot populations are threatened with extinction due to habitat loss and collection for the pet trade. The loss of nest trees and chick poaching can drastically reduce reproductive success. However, due to the long life span of many parrots, populations are unlikely to become extinct rapidly even with complete reproductive failure. For parrots that travel in family groups, rapid estimates of reproductive success can be obtained by recording group sizes in areas where they congregate. We used roost counts over an 18-month period to estimate the size and productivity of a population of Yellow-naped Parrots ( Amazona auropalliata auropalliata ) in Costa Rica. Up to 300 birds were observed flying to roost on offshore islands near Curú National Wildlife Refuge. Roost counts were lowest during the breeding period (December–March), increased after fledging (April–July), and peaked during the late wet season (September–October). Increased food availability on the islands during the breeding season allowed the parrots to become seasonal island residents, and lowered roost counts during that period. We calculated reproductive parameters by assuming that groups of >2 birds were adults traveling with young. The percentage of young in the population was 12.5% and did not differ between years. Studies of group size in birds that form stable family groups, such as psittacines in the genera Amazona and Ara , are an inexpensive way to obtain estimates of the reproductive output of some parrot populations and determine if further study or intensive management are warranted.     

Age bias in the bag of pink-footed geese <Emphasis Type="Italic">Anser brachyrhynchus</Emphasis>: influence of flocking behaviour on vulnerability

In pink-footed goose (Anser brachyrhynchus) wintering in Denmark, The Netherlands and Belgium, the proportion of juveniles in the hunting bag is consistently higher than that observed in the autumn population. Such juvenile bias in the bag is usually ascribed to young geese lacking experience with hunting or disruption of juveniles from families. An alternative explanation may be that flocking behaviour of families make juveniles more vulnerable. Observations of morning flights of pink-footed geese to the feeding grounds from two of the major autumn-staging areas showed that geese were distributed in many small flocks (median flock size = 9). This was not significantly different from the flock size distribution shot at by hunters (median = 8), suggesting that hunters targeted goose flock size in proportion to the general probability of encounter. The rate at which hunters downed geese was independent of flock size. The ratio between juveniles and adults in flocks decreased with flock size and flocks of <60 individuals primarily comprised family groups. The likelihood of being shot at was 2.4 times higher for juveniles and 3.4 times higher for older birds in small flocks (<10 individuals) compared to larger flocks. The observations suggest that both juveniles as well as successful adult breeding birds were more vulnerable than non-breeding/failed breeding birds as a result of flocking behaviour.     

Winter survival and breeding success of dominant and subordinate Willow Tits Parus montanus

We studied the effect of winter rank on survival rate and reproductive success in Willow Tits Parus montanus, a resident passerine living in dominance-structured flocks during the nonbreeding season, in 6 years. Winter survival was dependent on both the birds' age and rank. Adults survived better than first-year birds, and within first-year males, dominants survived better than subordinates. In other sex and age classes, rank did not contribute to survival. Although first-year males were in excess among nonbreeders, no connection existed between breeding status and rank. Female rank did not explain the variation in the start of laying, clutch size, number of fledglings or recruit production. We conclude that social status in Willow Tits affects individual fitness mainly through rank-dependent survival. Acquiring a high rank position seems to be most important for first-year birds, especially first-year males.     

Common Myna Roosts Are Not Recruitment Centres

We studied communal roosting in the Common Myna (Acridotheres tristis) in the light of the recruitment centre hypothesis and predation at the roost. The number and sizes of flocks departing from and arriving at focal roosts were recorded over a two year period. We also recorded the sizes and behaviour of foraging flocks. We found that flock sizes of birds departing from roosts at sunrise were larger than those at the feeding site, suggesting that there was no recruitment from the roosts. Flocks entering the roosts during sunset were larger on average than those leaving the following sunrise, suggesting no consolidation of flocks in the morning. Flocks entering the roosts at sunset were also larger on average than those that had left that sunrise, although there was no recruitment at the feeding site. There was no effect of group size on the proportion of time spent feeding. Contrary to expectation, single birds showed lower apparent vigilance than birds that foraged in pairs or groups, possibly due to scrounging tactics being used in the presence of feeding companions. Thus, the recruitment centre hypothesis did not hold in our study population of mynas. Predation at dawn and dusk were also not important to communal roosting: predators near the roosts did not result in larger flocks, and resulted in larger durations of arrival/departure contrary to expectation. Since flock sizes were smallest at the feeding site and larger in the evening than in the morning, but did not coincide with predator activity, information transfer unrelated to food (such as breeding opportunities) may possibly give rise to the evening aggregations.     

Territory occupancy and breeding success of Peregrine Falcons Falco peregrinus at various stages of population recovery

Organochlorine pesticides disrupted reproduction and killed many raptorial birds, and contributed to population declines during the 1940s to 1970s. We sought to discern whether and to what extent territory occupancy and breeding success changed from the pesticide era to recent years in a resident population of Peregrine Falcons Falco peregrinus in southern Scotland using long‐term (1964–2015) field data and multi‐state, multi‐season occupancy models. Peregrine territories that were occupied with successful reproduction in one year were much more likely to be occupied and experience reproductive success in the following year, compared with those that were unoccupied or occupied by unsuccessful breeders in the previous year. Probability of territory occupancy differed between territories in the eastern and western parts of the study area, and varied over time. The probability of occupancy of territories that were unoccupied and those that were occupied with successful reproduction during the previous breeding season generally increased over time, whereas the probability of occupancy of territories that were occupied after failed reproduction decreased. The probability of reproductive success (conditional on occupancy) in territories that were occupied during the previous breeding season increased over time. Specifically, for territories that had been successful in the previous year, the probability of occupancy as well as reproductive success increased steadily over time; these probabilities were substantially higher in recent years than earlier, when the population was still exposed to direct or residual effects of organochlorine pesticides. These results are consistent with the hypothesis that progressive reduction, followed by a complete ban, in the use of organochlorine pesticides improved reproductive success of Peregrines in southern Scotland. Differences in the temporal pattern of probability of reproductive success between south‐eastern and south‐western Scotland suggest that the effect of organochlorine pesticides on Peregrine reproductive success and/or the recovery from pesticide effects varied geographically and was possibly affected by other factors such as persecution.