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Late egg-laying and fledgling in a polyandrous trio of Bearded Vultures (Gypaetus barbatus) in the Pyrenees
Abstract
El dilatat cicle reproductor del trencalòs fa que les dates de posta d'aquesta espècie als Pirineus es concentrin entre la darrera setmana de desembre i la primera de febrer. L'envol del poll té lloc entre la segona quinzena de juny i primera setmana de juliol. La present nota documenta una posta i envol tardans en un trio poliàndric de trencalòs. L'any 2002 la posta, d'un sol ou, va tenir lloc entre el 13-16 de febrer. L'eclosió es va produir entre els dies 6-10 d'abril i el poll va abandonar el niu entre els dies 18-20 d'agost, quan tenia 130-134 dies. Aquest cas esdevé una de les postes exitoses més tardanes observades i l'envol més tardà documentat a la vessant sud dels Pirineus.
... Breeding occurs from December to September in Europe and northern Africa; October-May in Ethiopia; May-January in southern Africa; year round in much of eastern Africa; and December-June in India (Ferguson-Lees and Christie 2001). Eggs are incubated for 54 days on average and nestlings fledge after almost four months in the nest (Margalida 2002). In the case where two eggs are laid, obligatory 'cainism' occurs in which the older sibling kills the younger (Thaler and Pechlaner 1980), a common trait in larger raptors. ...
... Direct persecution (belief-based use). At least four cases of direct persecution of Egyptian Vultures are known from West Africa (Nikolov 2014 while 15-16 individuals of this species have been shot in Macedonia between 1983-2002(Grubac et al. 2014. ...
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... Belamendia). Entre el 25 y 28 de agosto de 2015 se observa que vuela un pollo de quebrantahuesos del nido de la unidad reproductora (UR) nº 67 en el término Municipal de Biescas, Huesca, que junto con la observación del vuelo del pollo el 15 de agosto de 2010 de la UR nº 1, Hecho, Huesca, suponen las fechas más tardías conocidas de vuelos de pollos en el Pirineo, ya que Margalida (2002) posee una observación del vuelo de un pollo entre el 18 al 20 de agosto. (J. A. Gil y J. C. Ascaso/Fundación para la Conservación del Quebrantahuesos). ...
To study the post-fledging period of the bearded vulture seven birds were wingtagged and raddiotagged before they left the nest. The bearded vulture has one of the longest post-fledging periods in birds. The end of this period seems realted to the beggining of the next breeding season of the adults, although sometimes it is extended while the adults are again incubating.
During the post-fledging period, the young stay around a small area near their parents ossuaries, were they are feed and roost. Pre dispersal flights last one or more days, travelling up to 24 km. In these flights there are not usually joined by the adults. Juvenile dispersion seems to take place towards the East, maybe due to a driffting effect of the prevailing winds.
As other authors we have not seen the young taking or eating food from wild carcasses. Although bone breaking seems to be a congenital behaviour, we have seen youf trying to break bones on the grass. This suggest that they start independence with little efficiency in finding and preparing food, and so an increase of mortality is expected at the beggining of juvenile dispersion
Bearded Vultures Gypaetus barbatus began supplying material to their nests on average 111 d (range 91-126 d) prior to laying. Males were significantly more active that females. Heavy material (branches) was transported indistinctly in the talons or in the bill while lining (wool) was generally transported in the bill. 71% of the wool was recycled from remains fallen from other nests, probably due to the scarcity of this material in relation to its importance for insulating the egg and chick from the low winter temperatures. No inter-sexual differences were observed with regard to the type of the material selected or how it was carried to the nest. The early nest-building behaviour and the fact that the males were the most active builders are discussed in the context of maintenance of the pair-bond and female selection. After laying, material for nest-maintenance was only rarely supplied, suggesting high solidity of the structure at its location at protected sites.
We describe copulation activity by Bearded Vultures (Gypaetus barbatus) at nesting sites in the Pyrenees, northern Spain, between 1993 and 1995. Pairs copulated for an average period of 67 days (range: 50-90) prior to egg laying. Seventy-five percent of attempts ended in successful copulation. Pairs displayed a daily bimodal pattern of copulation, with copulations occurring most frequently in the evening. Low levels of opportunities for extra-pair encounters (0.02 intrusions hr-1) were obtained despite the high density of reproductive individuals present. The high copulation rate observed may be explained by the potential risk of extra-pair copulations occurring while a member of the pair is away foraging, an activity which takes up as much as 65% of time each day. This species also showed a pattern of pair attention similar to that of other species of raptors in which males guard their females during the fertile period.
Monogamous biparental care is expected to occur when opportunities for extra-pair copulations are rare, and both parents are required to raise the chick. Bearded Vultures Gypaetus barbatus fulfill these conditions. Contributions by male and female Bearded Vulture to nest building, nest defence, incubation, nest attendance and chick feeding were studied over five years in eight pairs from the Pyrenees [Catalonia, northeast Spain). Overall, the sexes show equal investment, although the degree of parental effort developed differs depending on the specific activities. During pre-laying, males were significantly more active than females in supplying material to the nest and in territorial defence behaviour, which increased (in both sexes) as the season advanced. Incubation was shared equally both by day and by night. During chick-rearing, the nest was attended by both sexes and the presence of both parents at the nest decreased in parallel with the growth of the chick. Activities related to chick feeding were also equally divided. These results are discussed in the context of female selection of mates and the particular ecology of this species.
Evolution in the breeding rates of Bearded Vulture (Gypaetus barbatus) in Catalonia (N.E. Spain). The evolution of the Bearded Vulture distribution in Catalonia, decreased progressively from the beginning of this century until the 70's, and started a slow recovery of population in the 80's. Differences in density are found between the occidental area and the oriental one. Food and nest-site availibility are possibly the most important limiting factors. Breeding success, productivity and percentage of pairs that raise young succesfully analyzed from de 80's until now, reflects a significant decrease motivated probably by human activities, interspecific and intraspecific relations. Based on the obtained results, the conclusion might be that the process of recolonisation is finishing.
The reestablishment of the breeding population of Gyps fulvus in a test area of 1300 km2 on the north side of the western Pyrenees (32-34 clutches in 1976, 155-156 in 1992) implied an important colonization of new sites from 1987 onwards. The spatial dispersal towards the east and the west of the range occured at a rate of 1km/year. The demographic evolution of the sites (arrival of new breeders) is different from one site to the other (6-7 increase, 4 decrease, 5 are abandoned). Breeding parameters have been calculated from 1976 to 1995, on the base of 777 clutches (2,7 % of second clutches, one third clutch) in two sites which received the status of Nature Reserve in 1975 (98 nests at a mean altitude of 850 m, 86 % facing west in cliffs colonized by Petrocoptis pyrenaica and invaded by Buxus sempervirens). 72 % if the clutches are laid in isolated nests. The laying period extends from 27.12 to 27.03. 50 % on 25.01 but the laying season starts earlier every year. The incubation period is 47-57 days (M : 51-53 days, n = 113), the chick period in nest before fledging is 113-159 days (M = 135 d, n = 103). Consequently a nest is occupied on average between 188 and 365 days a year. The breeding success (S.R. in the French text) can vary from 0,40 fledgling/clutch/year to 0,95 (M = 0,76). 68 % of the abandoned nest are due to a failure during the incubating period (75 % of the cases). 80 % of the failures are due to persistent bad weather (heavy rainfalls, long period of snow melting). The S.R. is more important when the nest density is higher. The nests occupied more than 5 consecutive years have a breeding success higher than average. The annual productivity of juveniles is not directly correlated to the amount of food laid on the feeding site in Ossau (which was operated as soon as 1969). As this feeding site is intensively visited by the vultures from November to January (and not in March-April), it suggests that before breeding the birds search a source of regularly available carrion. The most probable hypothesis is that spatial expectation encourages the sedentariness of birds which don't have to go on uncertain foraging trips. During the ovogenesis (M = 24-27 days ; n = 16 ; min : 16d ; max : 38d) sedentariness is a positive factor for the synchrony of activity rhythm of the mates. Pairs can then spend time on the daily activities of the breeding cycle (mating, nest building and nest defense) in order to lay their eggs. The demographic consequences of the conservative management (artificial feeding place, creation of the Réserve Naturelle d'Ossau by the Parc National dels Pyrénées) on the recruitment of new breeders and the reproductive success are discussed in this paper.
From 1985 to 1998, 97 Circus a. aeruginosus tagged as chicks (50 males, 47 females) have been controlled as breeding birds on the "Ile d'Oleron" (Charente-Maritime) on 303 occasions. Data collected on the breeding behaviour (pairing, polygamy, breeding site, time at which the first egg is laid, number of eggs laid, and breeding success) is analysed in relation to the age of breeding birds.
We studied the diet of a pair of Bearded Vultures during the breeding season. as well as their selection of food regarding the carcasses theoretically available within the home range of the pair. The methodology used was based on direct observations of the prey brought to the nest, given that the collection of remains at the nest overestimates the importance of big bones and that the analysis of pellets (which are scarce and occasionally recycled) tends to underestimate the importance of large prey. Food availability was estimated from the mortality rates of the species of livestock present in the home range of the pair. Such livestock species accounted for 90% of the consumed prey. Sheep and goats accounted for 59% of the 64 prey which could be identified. Domestic rabbits accounted for a further 25%, cows and mares 3%, and pigs 3%. Only 51% of the prey delivered to the nest (n = 75) were bones. The pair selected sheep, goats and domestic rabbits, and tended to avoid cows, mares and pigs. Patterns of food selection appeared to be conditioned by the biomass provided by each prey type, as well as by the mean body size and predictability of such prey. Nevertheless, the likely differences in diet between the breeding season and the rest of the yearly cycle should be taken into account.
The growth of the chicks and pattern of feeds to the chicks were studied for Wandering Albatross pairs (Diomedea exulans) with (1) no previous breeding experience, (2) a limited experience, and (3) an extensive experience. Chicks of inexperienced pairs grew more slowly than those of experienced pairs only during the first part of the fledging period and they had similar dimensions and weights when they left the colony. These differences resulted from different patterns of food delivery to the chicks during the first part of the fledging period; chicks of inexperienced pairs being fed less regularly but with larger meals than those of experienced pairs. The patterns of chick feedings were similar in the two categories during the second part of the fledging period. There was no difference between the feeding patterns for chicks of pairs with either an extensive or a limited experience and small differences in growth appeared only during the first weeks of life of the chicks, probably because of differences in egg size. These results suggest that first-time breeders are slightly less efficient at feeding the chick than experienced birds, but they attain similar skills within a few months, and pairs do not increase their efficiency after a first fledging attempt.
Brown, C. J. 1990. Breeding biology of the Bearded Vulture in southern Africa, Part I: The nestling period. Ostrich 61: 24–32.
The nestling period of the Bearded Vulture Gypaetus barbatus in southern Africa was 124–128 days. The hatching interval between the normal two-egg. clutch was usually 3–6 days (range 2–9 days Only one nestling per clutch survived to the third day. Tittle sibling aggression and no infanticide took place, but the older nestling dominated the younger which obtained no food. For the first 40 days the nestling was closely brooded. The nest duties were evenly shared by both parents, but females brooded at night. Food was brought to the nest usually once or twice per day by both parents, and was stored behind the nest. During days 41–90 parental attendance steadily decreased. Dunng this stage the female spent more time in the nesting area (57%) and on the nest (91%) than the male. Towards the end of this stage the nestlin started to feed itself but preferred to be fed by a parent. From da 91 to first flight the nestling was left unattended and was visited by its parents only to provide food, which it fed from itself. All pars monitored (40 pair-years) attempted to breed every year. The breeding success (n = 18 pair-years) was 0,89 young fledged per pair per year.
Brown, C. J. 1990. Breeding biolo of the Bearded Vulture in southern Africa, Part I: The pre-laying and incubation periods. Ostrich 61: 24–32.In southern Africa the Bearded Vulture Gpaetus barbatus lays its eggs in mid-winter. between the second half of May and the first week of July. Pairs became more active in their nesting areas about six weeks before laying and usually roosted there at night. Courtship flights were less frequent and demonstrative than in Eurasian birds and took place mainly in the late afternoons. During the pre-laying period most nest visits (77%) were to bring nesting material, 92% by the male. All nesting material was arranged by the female. Copulation was always preceded by allopreening, and occurred most frequently in the mornings. No copulation or courtship display took place after the first egg had been laid. Of 18 clutches, 16 (89%) contained two eggs and the remainder one egg. The laying interval was usually 3–5 days (range 2–9 days). Incubation started with the first egg and was evenly shared by both parents during the day, but only the female incubated at night, individual pairs maintained distinctive nest attendance and foraging period timetables, which allowed sufficient time for self-foraging by both parentes. No food was brought into the nest during the pre-laying and incubation periods, but in some pairs food was cached in nearby potholes in cliffs. The incubation period was 56–57 days.
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