One Norwegian territory of the Marsh Tit Parus palustris during 35 years

One Norwegian territory was occupied by successive pairs of Marsh Tits Parus palustris during 35 breeding seasons. Only ten males and seven females were involved. Each pair showed strict site fidelity and kept to the territory all year round. The pair bond lasted throughout life, and the duration varied from one to eight successive years. The number of successive mates varied for the males from one to two females and for the females from one to four males. Assuming that the birds were juveniles or 1 year old when ringed, they survived, on the average, 4.4 years. The oldest male survived for at least 10 years 4 months and the oldest female for 8 years 4 months. The mean survival rate of adults from one breeding season to the next was 75.8%, which is remarkably high when compared with the genera! findings in tits.     

Identification and breeding of yearling Piping Plovers

ABSTRACT Age of first breeding is an important life history trait. Many Piping Plovers (Charadrius melodus) do not breed as yearlings, but little information is available concerning the age of first breeding. From 2000 to 2006, we marked 991 chicks in three areas in Saskatchewan, Canada, and subsequently determined when 102 (49 females and 53 males) first bred. Females bred significantly earlier, on average, than males. More females (68%) bred as yearlings than did males (41%; P= 0.04), with most others first nesting when 2‐yr old (29% of females and 50% of males). As expected from differences between the sexes in age of first breeding, younger females were more likely to pair with older males than were younger males with older females. Chicks that hatched early in the breeding season did not breed at an earlier age than those that hatched late in the year. Unlike older birds, juvenile Piping Plovers do not replace flight feathers during their first winter. As a result, 18 of 27 yearlings (67%) had worn outer primaries, whereas only one of 123 (1%) older birds had worn primaries. In addition, whereas 20 of 24 yearlings (83%) retained a few buff‐tipped median coverts, none of 119 known older birds had such coverts. As a result, we were able to identify all yearlings by their worn primaries, buff‐tipped median wing coverts, or both. Wing lengths of yearling Piping Plovers were 3% shorter than those of older birds, presumably due to wear. Because there is no evidence of differences in adult survival rates between the sexes and breeding habitat is available, we speculate that fewer yearling males than females breed because primary wear may reduce the ability of yearling males to perform aerial breeding displays.     

Male‐skewed adult sex ratio,survival, mating opportunity and annual productivity in the Snowy Plover Charadrius alexandrinus

Sex differences in adult mortality may be responsible for male‐skewed adult sex ratios and male‐skewed parental care in some birds. Because a surplus of breeding males has been reported in serially polyandrous populations of Snowy Plover Charadrius alexandrinus, we examined sex ratio, early‐season nesting opportunities, adult survival and annual reproductive success of a Snowy Plover population at Monterey Bay, California. We tested the hypotheses that male adult survival was greater than female survival and that a sex difference in adult survival led to a skewed adult sex ratio, different mating opportunities and different annual productivity between the sexes. Virtually all females left chicks from their first broods to the care of the male and re‐nested with a new mate. As a result, females had time to parent three successful nesting attempts during the lengthy breeding season, whereas males had time for only two successful attempts. Among years, the median population of nesting Plovers was 96 males and 84 females (median difference = 9), resulting in one extra male per eight pairs. The number of potential breeders without mates during the early nesting period each year was higher in males than in females. Adult male survival (0.734 ± 0.028 se) was higher than female survival (0.693 ± 0.030 se) in top‐ranked models. Annually, females parented more successful clutches and fledged more chicks than their first mates of the season. Our results suggest that in C. alexandrinus a sex difference in adult survival results in a male‐skewed sex ratio, which creates more nesting opportunities and greater annual productivity for females than for males.     

The life cycle of the Upland Goose Chloëphaga picta in the Falkland Islands

Upland Geese Chloëphaga picta were studied between 1977 and 1980, primarily around Darwin, East Falkland, in order to describe their breeding biology, moulting and adult survival. The population of breeding birds in a valley reached a peak from mid-September to late November when nesting took place. The average territory length was 240 m in five valleys. Breeding adults generally returned to breed in the same territory each year and with the same mate. Nests were on the ground, usually amongst whitegrass Cortaderiapilosa. The mean clutch size was 6-1, brood size was 5-1 and fledged family 3–9. Incubation took 30 days and the fledgling period was about 70 days. Most broods were raised in the nesting territory. Growth of goslings is described. The breeding success between laying and fledging was 0–34 (in 1977) and 0–29(in 1978), giving an annual production of 21 and 1–8 young per breeding pair. Fledglings remained in family parties through the autumn and winter and were evicted by their parents in early spring. Some siblings stayed together for short periods and then joined other non-breeders. Females started pairing at ten months of age and most were paired at 17–18 months. Some bred for the first time at 23 months. Males started pairing at about 20 months of age. Flightless moult (shedding) took place at ponds or in sheltered inlets of the sea, in flocks of up to several hundred birds. Flightless birds were found between 14 November and 11 February, though 50% were flightless between 26 November and 2 January. Individuals were flightless for 36 days. First-year birds were more synchronized in shedding than adults. The percentage of first-year males (in the male component) varied from 16-5 to 45-9% in shedding flocks, and significantly more males were present in some flocks. The flocks were composed of first-year and second-year birds too young to breed and failed breeders. The percentage of a shedding population which returned to the same site in successive years was 25-3 and 15-1% at two localities. The moult of other feather tracts is described. The annual survival rate of breeding adults was 82%. A model of the population dynamics is presented. The current level of culling to control the goose population is less than the number which must die each year to maintain a stable population.     

Breeding site fidelity and natal philopatry in the Redshank Tringa totanus

This paper presents the results of a study carried out on breeding Redshank in the Ribble Marshes, Lancashire, England.
Redshank tend to return to the same breeding area year after year. There was no detectable sex bias in return rates. Experienced birds were more site faithful than inexperienced birds, with previously successful birds exhibiting the highest degree of breeding site fidelity. Older, more experienced birds were more successful at hatching eggs than inexperienced birds.
Breeding dispersal was the same both within and between years. Faithful pairs and males nesting with a new mate dispersed significantly shorter distances than females nesting with a new partner. Dispersal distances in female Redshank were affected by breeding success: unsuccessful females, nesting with a new mate, dispersed significantly farther than successful females. A pair's breeding success influenced the following year's mate fidelity. However, other factors such as overwintering survival and date of return may also have influenced mate fidelity.
Redshank were highly faithful to their natal area; a high proportion of birds that survived post-fledging mortality returned to breed in their area of birth. No sex bias in natal dispersal was detected. Approximately 50% of Redshank breed in their first year of life.     

FACTORS AFFECTING THE AGE OF FIRST BREEDING OF THE KITTIWAKE RISSA TRIDACTYLA

At a Kittiwake colony in Northumberland, 80% of those birds which returned to their natal colony to breed were males and these supplied 52% of all male recruits. More females breed away from their natal colony than males. There was no differences in the proportions of young fledged from sites in the centre or at the edge of the colony, or by parents of different experience, which returned to breed. Kittiwakes breed for the first time at ages from 3 to 8 years, but most at 4 or S years old. Males arrive back at the colony at an earlier age than females and breed for the first time one year earlier. Males obtaining sites at the centre of the colony first breed at an earlier age than those at the edges. Neither the age nor the area of first breeding appear to be transmitted from parent to offspring. Males breeding first aged 4 years or younger produced more young than those which first bred aged 5 years or older, despite their partners laying smaller clutches. This difference was most marked among those males recruited to sites in the centre of the colony. The advantage of this earlier breeding is counteracted by a lower survival rate among those males which start to breed at the younger ages. In all breeding Kittiwakes, annual reproductive output increases with experience while annual survival rates decrease. Once they had started to breed, many birds failed to breed in one subsequent season. Nearly 60% of these cases of intermittent breeding occurred in the year following first breeding. Intermittent breeding was most frequent among young birds and among females. It is suggested that each breeding involves a cost to the individual in terms of reduced survival, and that deferred and intermittent breeding are means of guarding survival. A model is proposed whereby the age at which a bird starts to breed, the nesting site which it obtains, and its subsequent breeding strategy result in each individual producing an optimal number of reproducing offspring in its lifetime, relative to its quality.     

High survival rate and site fidelity in the Siberian Tit Parus cinctus, a focal species of the taiga

The Siberian Tit Parus cinctus population of Finland, and probably of the whole of Fennoscandia, has declined dramatically during this century. Understanding its population dynamics is essential for its conservation. We studied annual survival rate and dispersal distance of both breeding and fledgling Siberian Tits during 1989-97 in a moderately managed forest habitat near the southern border of its range in Kuusamo, northeastern Finland. Breeding density was low, averaging 0.51 pairs/km in a nestbox area of about 42 km². This was probably an underestimate, because we did not search for nests in natural holes. However, following its population decline, overall densities at the southern border of the range are low. The study area was, however, suitable breeding habitat as reflected by their high nesting success. Brood size at fledging averaged 7.45 young, and reproductive output was 6.16 young per breeding pair, including failed nests. Clutch size adjustment was successful among pairs producing fledglings because, on average, 92.6% of the eggs laid produced young in successful broods. Median distance between consecutive breeding attempts was 100 m for both males and females (range 0–2500 m and 0–6000 m, respectively). Natal dispersal distance was significantly longer in females than in males. We applied Cormack-Jolly-Seber modelling to estimate survival and recapture probabilities separately. Survival of breeding birds was not sex-related, averaging 0.69 annually. Some of the ringed fledglings (3.0%) were later captured as breeders in the area. This is an underestimate of local survival rate due to incomplete recapturing of breeding birds. The implications of these results with respect to the conservation status of the species are discussed.     

Breeding dispersal and site-fidelity in three monogamous wader species in the Western Isles, U.K.

Adult and post-natal breeding-dispersal movements of Redshank Tringa totanus , Dunlin Calidris alpina and Ringed Plover Charadrius hiaticula were quantified in west Scotland. Data from 373 returning birds marked as breeding adults and 142 returning birds marked as chicks are presented. Unlike most previous studies, this study measured dispersal movements up to 40 km and attempted to overcome distance-related biases. For each species, adult males were significantly more nest site-faithful between years than were adult females. Likewise, first-time breeding males bred significantly closer to their natal site than did females. The settlement intensity per unit area of habitat showed marked differences between species, age classes and sex in the relative attractiveness of potential areas at different distances to settling birds. Adult dispersal was negatively and significantly related to breeding success in the previous year and positively related to capture on the nest in the previous year. Dispersal movements of adult Ringed Plover breeding on unstable cultivated habitats were significantly related to habitat quality (measured in terms of nest survival) and were always to habitat of better or equal quality.     

POPULATION,DIET AND THE ANNUAL CYCLE OF THE LAUGHING DOVE AT BARBERSPAN,PART 3: THE ANNUAL CYCLE

Dean, W. R. J. 1979. Population, diet and the annual cycle of the Laughing Dove at Barbers-pan, Part 3: The annual cycle. Ostrich 50:234-239.

Laughing Doves Streptopelia senegalensis were collected each month from July 1976 to June 1977. In each sample some males and females were breeding. Breeding and primary moult overlapped, and some birds began to moult after starting to breed, and began to breed after starting moult. Adult Laughing Doves require about 120 days to complete primary moult, and juveniles require about 90 days. Weights of moulting birds were not significantly different from those of non-moulting birds, and there were no seasonal trends in the weights of either group. The mean weight of 79 males was 101,6 g and of 39 females was 100,2 g.     

SURVIVAL,PAIR BOND RETENTION AND NEST-SITE TENACITY IN BULLER'S MOLLYMAWK*

Adult Buller's Mollymawks Diomedea bulleri banded in 1948 and 1961 at the Snares Islands south of New Zealand have been recovered between 1961 and 1971. Survival curves are presented which indicate the existence of a constant annual mortality rate of not more than 11.1 % with a mean expectation of further life at the time of banding of not less than 8.5 years. Breeding birds show a strong tendency to retain both the pair bond and the nest-site. One pair was still breeding in 1971 at the same nest at which it bred 23 years earlier. No re-matings were recorded while the original partner was known to be still alive. The dimensions of eggs laid over the years by particular females are presented. These enable some general indications to be given of the effects of the age of the female on the dimensions of the eggs which she lays.     

ECOLOGY OF THE COMMON BABBLER TURDOIDES CAUDATUS

Some aspects of the ecology and behaviour of the Common Babbler are described. The species resembles most other members of the genus Turdoides in being group territorial and exhibiting cooperative breeding. Females remain with their natal group until 6–9 months old and then disperse. Males, in most cases, remain indefinitely in their natal group so that these essentially constitute male clans. In half of the groups observed only a single pair bred per season, but in some large groups two pairs attempted to breed, one always being unsuccessful, and in other cases one male bred successively with two different females. Overall breeding success was highest for groups in which successive polygyny occurred. Male non-breeders fed the nestlings more often than female non-breeders which were sometimes driven off by the breeding female. A positive correlation was found between the number of non-breeders feeding the nestlings at day 9–11 and the size of the brood. This probably did not indicate a causal relationship. Breeders in large groups continued to moult while breeding, while those in small groups arrested their primary moult. This difference suggests that assistance from non-breeders may have had some effect in reducing the physical strain on the breeding pair. Observed overall survival of adult birds was 63% per annum, but that of the breeding males was 88% per annum. The population declined by 19% during the period of the study, suggesting that observed rates of survival may have been lower than normal.     

The pair bond and divorce among Oystercatchers Haematopus ostralegus on Skokholm Island, Wales

Mate changes of Oystercatchers were followed over a 15-year period. In 8.0% of instances, the pair split up between breeding seasons even when both members bred the second season. The likelihood of divorce was highest for birds aged five years, the modal age of first breeding. After divorce birds did not select an older or younger mate when re-pairing. Low hatching success increased the chances of divorce. Divorce was not followed by significant changes in clutch-size, laying date or nesting success (although females tended to be more successful).     

Age-related fledgling production in great cormorants Phalacrocorax carbo: influence of individual competence and disappearance of phenotypes

Age-related reproductive performance of great cormorants Phalacrocorax carbo sinensis was studied in a tree nesting colony in Denmark in relation to age-related improvements of competence and progressive disappearance of phenotypes. Within-individual changes in fledgling production were measured, and cross-sectional analyses were applied. The within-individual analyses showed that competence improved with age and/or that individuals showed restraint to optimize their reproductive effort. The within-individual improvements were three to six times higher among individuals that survived and returned to breed beyond the fourth breeding attempt than among individuals disappearing from the breeding population before the fourth breeding attempt. Taking this into account the within-individual improvements explained 70–90% of the age-effect observed in the population over the youngest ages. Effects of breeding experience were significant for females, but only within the group of individuals that were present in the breeding population beyond the age of five years. In males, improvements arose because of unknown factors related to age. Individual great cormorants that bred beyond the age of five years had higher reproductive success, on average, than birds disappearing from the breeding population earlier in life. This supports the differential survival hypothesis. However, the effect on the population mean was partly counterbalanced by late recruitment of other inferior breeders. It is concluded that the enhancement in fledgling production with increasing age was primarily an effect of age-related improvements of competence and secondly an effect of progressive disappearance of phenotypes.     

Pair bond and breeding success in Blue Tits Parus caeruleus and Great Tits Parus major

Data from 939 nests of the Blue Tit Parus caeruleus and 1008 nests of the Great Tit P. major from nestboxes provided in superabundance in mixed forest study sites between 1976 and 2001 were analysed to examine the effects of mate retention on breeding success and the relationship between mate fidelity and site fidelity. Most birds retained their former partner (76% in Great Tits and 65% in Blue Tits). The probability of a pair divorcing was affected by male age in Great Tits, divorce being more likely in pairs with first‐year males. Great Tit pairs breeding together for a second season bred earlier, but had no higher breeding success than pairs breeding together for the first time. In Blue Tits laying date and start of incubation tended to be earlier in pairs breeding together for a second season, but hatching and fledging dates were not earlier than in other pairs. Great Tit pairs breeding together for two consecutive seasons bred earlier in the second season than in the first, but breeding success did not differ significantly between years. In both species, breeding performance did not differ between pairs that divorced after a season and pairs that stayed together. Thus breeding success did not determine whether a pair divorced or bred together again. Neither Blue Tits nor Great Tits improved their breeding performance through divorce. Blue Tit females even had fewer fledglings in the year after divorce than in the year before. Mate retention affected breeding site fidelity. Blue Tit females had greater breeding dispersal distances between consecutive years when re‐mating than when breeding again with the same mate. In Great Tits both males and females dispersed more when re‐mating than when retaining the former partner, suggesting that mate retention increased the chance of retaining the breeding site. In both species, breeding dispersal distances did not differ between pairs that divorced and pairs in which one mate disappeared. Because no major advantage of mate retention was evident, we suggest that mate retention evolved under different conditions than those found in study sites with high breeding densities and a superabundance of artificial nesting sites.     

Turnover and dispersal in a Peregrine Falco peregrinus population

In south Scotland, most Peregrines returned to the same territories to breed in successive years, though a few females changed territory from one year to the next.
Annual mortality among breeding birds was at most 9% among females (or 11% in both sexes combined). There may have been considerable annual variation, however, and excluding one exceptional year out of five reduced the estimate for females to 7%. These estimates are maxima, but are still considerably lower than those obtained from ring recoveries of dead birds reported by members of the public.
Among trapped birds, four males first bred at age two years, one at three and another at four or five; two females first bred at one year, 13 at two years old and one at three. Five other females which were seen to be in first-year plumage but were not trapped, also laid eggs, and 12 other such paired females held territory but did not lay. Only one paired male held territory in first-year plumage.
In their movements between natal and breeding territories, some females moved further than males, with median distances of 83 and 58 km respectively. In addition, of birds trapped breeding in the study area, a greater proportion of the males than of the females had been born locally, despite an equal sex ratio among fledglings; this was also consistent with a greater dispersal of females. In general, Peregrines made much longer movements in their first year of life than subsequently. Movements were in any direction.     

Survival in king penguins Aptenodytes patagonicus: temporal and sex-specific effects of environmental variability

We investigated annual adult survival rates of king penguins Aptenodytes patagonicus breeding at South Georgia during 6 years in relation to age/breeding experience, sex, and food availability. During the first 3 years of the study, when food availability was good, survival was 97.7% for experienced breeders, which confirmed the very high survival rates observed in penguins in general. In these years survival did not differ between the sexes, presumably because parental investment is shared equally between the sexes, and the sexual dimorphism is small in king penguins. Survival was lower for young, first-time breeders (83.0%). In experienced birds the annual survival rate decreased to 68-82% following a catastrophic year when food availability was extremely low. We address the question how parents balance their current investment in offspring against their chances to reproduce in the future. We argue that the high mortality rate among breeding individuals after the year of food stress provides support for previous suggestions that the response to increased costs in seabirds might be complex to predict and does not always follow intuitive expectations according to general life-history theory. We also found that females survived significantly less well than males following the bad year. We explain this result as follows: the male-biased sex ratio (56:44) that we observed in our study colony clearly does not result from lower female survival during normal conditions. An already existing skewed sex ratio forces males to delay the onset of breeding because of a lack of breeding partners. This in turn causes breeding females to be, on average, younger and less experienced than males and to have lower survival following a year of food shortage. In this study survival was linked with food availability and we suggest that this was connected to climatic/oceanographic features, such as the position of the Antarctic Polar Front Zone. We could, however, not verify this by anomalies in sea surface temperature data.     

Movements of Eiders Somateria mollissima on the east coast of Britain

Movement patterns, sex differences in natal dispersal and breeding dispersal, and interchange of birds between colonies were studied in the population of Eiders Somateria mollissima breeding on the east coast of Britain. First-winter Eiders reared at the Sands of Forvie, Grampian, remain at or close to the colony, while most adults move about 100 km south to winter on the Firths of Forth and Tay. A proportion of the Forvie population is sedentary. Eiders which breed in Northumberland either move north to winter on the Tay and Forth estuaries or remain close to their breeding areas. Eiders breeding in Fife are sedentary. Recoveries of British-ringed Eiders in Scandinavia indicate that some British-born males join the Baltic breeding population, probably by pairing with Scandinavian females wintering in Britain. There is extensive natal dispersal of males from Forvie, with more than twice as many Forvie-bred females as males returning to the colony to breed. The breeding dispersal of males is also twice that of females. Dispersal of males from the relatively sedentary Forvie wintering population is less than that from the breeding population. Previous work suggested that at Forvie sedentary birds nesting close to the estuary were genetically isolated from migratory ones nesting along the coast. This situation is less clear cut than had been supposed previously, with many migrants nesting close to the estuary. It is unlikely that the genetic differences between females nesting in different parts of the Forvie colony will remain stable in the long term, due to the natal and breeding dispersal of males.     

Senescence and carryover effects of reproductive performance influence migration,condition, and breeding propensity in a small shorebird

Breeding propensity, the probability that an animal will attempt to breed each year, is perhaps the least understood demographic process influencing annual fecundity. Breeding propensity is ecologically complex, as associations among a variety of intrinsic and extrinsic factors may interact to affect an animal's breeding decisions. Individuals that opt not to breed can be more difficult to detect than breeders, which can (1) lead to difficulty in estimation of breeding propensity, and (2) bias other demographic parameters. We studied the effects of sex, age, and population reproductive success on the survival and breeding propensity of a migratory shorebird, the piping plover (Charadrius melodus ), nesting on the Missouri River. We used a robust design Barker model to estimate true survival and breeding propensity and found survival decreased as birds aged and did so more quickly for males than females. Monthly survival during the breeding season was lower than during migration or the nonbreeding season. Males were less likely to skip breeding (range: 1–17%) than females (range: 3–26%; β_sex = ?0.21, 95% CI: ?0.38 to ?0.21), and both sexes were less likely to return to the breeding grounds following a year of high reproductive success. Birds that returned in a year following relatively high population‐wide reproductive output were in poorer condition than following a year with lower reproductive output. Younger adult birds and females were more likely to migrate from the breeding area earlier than older birds and males; however, all birds stayed on the breeding grounds longer when nest survival was low, presumably because of renesting attempts. Piping plovers used a variety of environmental and demographic cues to inform their reproduction, employing strategies that could maximize fitness on average. Our results support the “disposable soma” theory of aging and follow with predictions from life history theory, exhibiting the intimate connections among the core ecological concepts of senescence, carryover effects, and life history.     

A population study of the Rook Corvus frugilegus in Leon Province, northwest Spain

A resident population of Kooks Corvus frugilegus in Leon, Spain, decreased by 247; from 197679. Migrant Rooks appear not to enter the range of this population which is unique in the Iberian Peninsula. During the breeding seasons colonies are attacked by man: 17–19% of birds failed to breed and only 0.5-0.7 young per nest survived to fly. The trees chosen for nesting are in plantations subject to regular cropping, after which colonies are scattered. Adult mortality was 16–26% annually. Young formed 17.6–23% of the population in June; 11–15.6% of birds in March were in their first year and many of these bred successfully. Communal roosts were used only from mid-July to mid-October.