First-year Birds Research Articles

Condition-dependent immune defence in the Magpie: how important is ectoparasitism?

The immune system has high costs of maintenance and production and expression of immune function should be dependent on the condition of the individual. The fitness cost that parasites impose on hosts may then be reflected in the investment that hosts make in immunity. Little is known about sources and consequences of intra- and interspecific variation in the presence and size of organs of the immune system in relation to ectoparasitism. Variation in the presence and size of the bursa of Fabricius and spleen size was measured to assess potential relationships between immune defence, nutritional condition and ectoparasites in the Magpie Pica pica. We found three species of lice (Mallophaga), two species of louse flies (Hippoboscidae), and the larvae of a tick (Ixodidae) infecting magpies. Age explained a significant proportion of variation in prevalence and number of parasite species, first-year birds being more parasitized than adults. Spleen size increased with nutritional condition, and the level of ectoparasitism negatively affected nutritional condition. Only one species of lice (Philopterus picae) was involved; the negative effect of this species on nutritional condition was more pronounced in males than females. These results are consistent with the hypotheses of condition-dependent investment in the immune system and sexual differences in susceptibility to parasite effects. Ectoparasites may thus play a role in modulating the relationship between condition and immune defence. We also found evidence for an interaction between the bursa and the spleen. Magpies with bursa had larger spleens than those where it had atrophied. This interaction did not affect ectoparasitism or nutritional condition.

Body mass of six long-distance migrant passerine species along the autumn migration route

We analysed body mass and moult data of six passerine species along their autumn migration route from northern Europe to North Africa and derived hypothetical models of the organisation of their migration in terms of fuel store accumulation. We analysed data of 46,541 first-year birds from 34 trapping sites, sampled in a network of collaborating European and African ringing stations. After accounting for effects of time of day and size, there were marked differences between the six species examined in the change of body mass along the migration route and in the timing of moult. Garden Warblers (Sylvia borin) and Pied Flycatchers (Ficedula hypoleuca) underwent their postjuvenile moult prior to migration and increased their average body mass along the migration route. Sedge Warblers (Acrocephalus schoenobaenus) also increased body mass towards the south, but started the migration bout without further refuelling well before the Sahara and moulted mainly in the wintering grounds. Reed Warblers (Acrocephalus scirpaceus) and Whitethroats (Sylvia communis) migrated while still moulting and did not increase average body mass towards south. They accumulated the energy needed to fly over the Sahara just before it. Spotted Flycatchers (Muscicapa striata) behaved in the same way, but contrary to Reed Warblers and Whitethroats they did not accumulate much fat stores in North Africa, which might urge them to stop and fuel up regularly in the Sahara. In the course of the season average body mass of all species increased slightly, which enabled them to migrate faster. In general, average body mass of first-year birds in northern and central Europe during the migration period was comparable to that of adults during breeding.

Primary moult, biometrics, mass and age composition of Grey Plovers Pluvialis squatarola in southeastern India

Little is known about the biology of waders wintering in southern Asia; this paper deals with the Grey Plover Pluvialis squatarola, a species extensively studied only in western Europe. Adult Grey Plovers wintering in southeastern India underwent primary moult in autumn; the duration was estimated to be 127 days, with mean starting date 1 September and mean completion date 5 January. Some first-year Grey Plovers initiated primary moult in late winter and spring, and completed this moult the following spring. The average mass of adults on arrival in September was 200 g, fluctuated close to 220 g from October to February, and increased to 280 g near the end of May. The mass variation did not show the January peak observed in western Europe. Breeding productivity, measured as the percentage of first-year birds in winter catches, varied between 5% and 70% over six years, and showed a positive correlation with that of Dark-bellied Brent Geese Branta b. bernicla in western Europe and Curlew Sandpipers Calidris ferruginea in South Africa.

Mortality and breeding failure of little penguins, Eudyptula minor, in Victoria, 1995 - 96, following a widespread mortality of pilchard, Sardinops sagax

In May 1995, numbers of little penguins, Eudyptula minor, coming ashore declined at Phillip Island and St Kilda concurrently with deaths of many penguins in western Victoria and a massive mortality of one of their food species (pilchard) throughout southern Australia. Among 1926 dead penguins reported were 131 banded birdsrecovered from Phillip Island (86% adults and 14% first-year birds), 26 from Rabbit Island and six from St Kilda. The number of banded penguins found dead per number of adult Phillip Island birds at risk was 2.3% in 1995 compared with an annual mean of 0.7% for 1970–93. Of 29 corpses autopsied, at least 26 died of starvation associated with mild–severe gastro-intestinal parasitism. Following the pilchard mortality, egg-laying by penguins in the subsequent breeding season (1995–96) was ~2 weeks later than the long-term mean and 0.3 chicks were fledged per pair compared with the long-term mean of 1.0. Unlike previous years, few penguins were recorded in Port Phillip Bay in September–October 1995, a period when pilchard schools were infrequently seen. It is concluded that the increase in penguin mortality in northern Bass Strait and the significant reduction in breeding success were associated with the widespread pilchard mortality.

Primary moult and body-mass of the Cape Turtle Dove Streptopelia capicola, and its abundance relative to the Laughing Dove S. senegalensis, in the Western Cape

Underhill, L.G., Underhill, G.D. & Spottiswoode, C.N. 1999. Primary moult and body-mass of the Cape Turtle Dove Streptopelia capicola, and its abundance relative to the Laughing Dove S. senegalensis, in the Western Cape. Ostrich 70 (3&4): 196–199. The duration of primary moult of adult Cape Turtle Doves Streptopelia capicola was estimated to be 192 days. 23 November was the estimated mean starting date, with 95% of birds starting within 88 days of this date. The mean body-mass of adults was 148 g and of first-year birds was 130 g. In residential areas, Cape Turtle Doves were trapped less frequently than Laughing Doves S. senegalensis; at most rural sites, Cape Turtle Doves comprised about two-thirds of the catch. On a dairy farm, where doves were attracted to cattle feed, 1 % of doves were Cape Turtle Doves. The emerging pattern is that Laughing Doves predominate at sites where food is provided on a long-term basis.

Age-related changes in wing-length and body mass in the Reed Warbler Acrocephalus scirpaceus and Clamorous Reed Warbler A. stentoreus

We studied the wing-length and body mass of the two populations of Reed Warblers (summer breeders and transients), and that of the resident Clamorous Reed Warbler, which exist in Israel. We found that, in all three groups, wing-length increases significantly with age for several years. Body mass also increased slightly (but significantly) with age. These differences were not caused by differential survival of juveniles, but appear to be a general phenomenon, possibly related to better nutrition of the adults. The autumn migration of transient Reed Warblers lasted from August until November, but no adults were captured during October and November, while 29.3% of the first-year birds were captured during these months. This suggests that adults can afford to start migration earlier, perhaps due to their greater experience.

Temporal, spatial and social segregation of red-billed choughs between two types of communal roost: a role for mating and territory acquisition

We assessed the value of communal roosting for mating and territory acquisition in nonbreeding red-billed choughs, Pyrrhocorax pyrrhocorax . Between 1991 and 1996 we surveyed all communal roosts, breeding territories and vacant nest sites in an area of 250km2in Los Monegros (northeast Spain), as well as other communal roosts in the surrounding 500km2from 1987 to 1996. Main roosts were used traditionally and throughout the year and gathered more choughs than subroosts, which were used only during the nonbreeding season. Nonbreeding choughs were socially segregated in these roosts according to their age and breeding prospects. Compared with random potential roost sites, main roosts included more first-year birds and were in areas of higher breeding density. Subroosts were mainly joined by choughs of breeding age (at least 2 years old) whose morphology (males) and body condition (females) were similar to those of established breeders, and were in areas with breeding densities as high as around main roosts but with more available nest sites. Nonbreeding choughs that used main roosts later used subroosts, while the converse was rare. More choughs joining subroosts acquired mates than those joining main roosts. Choughs mostly paired with roostmates but also with widowed territorial breeders. Finally, choughs from subroosts acquired territories closer to the roost than those who mated in main roosts, supporting the hypothesis that subroosts reduce the costs of mating and territory acquisition.

Use of ring recoveries to monitor long-term changes in the survival rates of British and Irish Cormorants Phalacrocorax carbo

Ring recovery data were used to assess changes in the survival rates of Cormorants in Britain and Ireland between 1965 and 1994. It was found that 99% were ringed as nestlings, thus necessitating an assumption of constant reporting rate across age-classes. The wide geographical spread of ringing effort since 1965 produced sufficient recoveries to enable analyses of trends in survival and reporting rates, but regional subdivisions of the data resulted in high sampling correlations between survival estimates. The assumption of a constant reporting rate across age-classes may be violated for British and Irish Cormorants, because first-year birds are more likely to be shot or caught in fishing nets than older birds and they have a differing seasonal pattern of recoveries. A simple simulation showed that first-year, but not adult, survival estimates were particularly sensitive to age-specific variation in reporting rates. However, the observed trend in first-year survival appeared robust to the assumption of constant reporting rates across age-classes. Declining reporting rates in Britain and Ireland imply that larger numbers of Cormorants will need to be ringed in order to monitor future changes in survival. Regional colour marking schemes for Cormorants have the potential to provide high quality survival information, to supplement that provided by dead recoveries and to offset the observed decline in reporting rates.

Breeding ecology of the fairy martin

The breeding biology of the fairy martin, Hirundo ariel, was studied over three years (1992–95) in the Yarra Valley, Victoria. Adult males and females in this population were morphologically similar, though only females acquired a brood patch during the breeding season. Colonies ranged in size from 8 to 29 nests. Birds arrived in the study area in September and usually commenced laying in October, though nesting activities were generally asynchronous both between and within colonies. Most colonies contained active nests until February. At least 16% of adults and 5% of fledglings, on average, returned to the study area in the following year. Returning adults generally nested at the same colony site as the previous year, while most first-year birds nested at sites other than their natal colony. Adult males were more likely to return than adult females. Clutch size ranged from 2 to 5, with a mean of 3.5, and declined over the season. The incubation period varied from 12 to 18 days with a mean of 13.7. A mean of 1.8 chicks fledged per completed clutch, while 60% of clutches produced at least one chick. The period from hatching to fledging varied from 17 to 32 days, with a mean of 22.1, and increased with brood size. Fledging success was highest during the middle of the breeding season. Adverse weather conditions, resulting in the abandonment of clutch and brood, were the most common cause of nest failure, and on several occasions also resulted in adult mortality. Almost half the breeding females produced at least two clutches in the one season. Pairs produced from 0 to 8 fledglings per season, with those that commenced nesting earlier in the season having higher annual productivity. These results are discussed in relation to the breeding ecology of other members of the Hirundinidae.

A method for studying post-fledging survival rates using data from ringing recoveries

We present a method for studying post-fledging survival rates from data on national ringing recoveries. The approach extends the classical two-age-class models of Brownie et al. (1985) to include a third age-class of birds ringed as nestlings. The models can incorporate age-class-specific and year-specific variation in reporting rates and survival rates. Unlike intensive resighting studies at single sites, this approach does not confound death with emigration and provides estimates of survival which are representative of a larger geographical area. We implemented the models with SURvIv software, using likelihood-ratio tests to assess the significance of possible age and year effects on survival rates or reporting rates. We demonstrate this approach using a set of data on British-ringed Song Thrushes Turdus philomelos. In this case, we were unable to detect any age-class-specific or year-specific variation in reporting rates and, although the survival rates of first-year and adult Song Thrushes varied significantly between years, post-fledging survival did not show any detectable inter-annual variation. Song Thrushes ringed as nestlings had a 0.38 chance (95% CI = 0.30–¸0.45) of surviving the 63-day post-fledging period (here defined as the period separating the average dates of birds ringed as nestlings and birds ringed as independent first-year birds).

Modelling survival rates in the Cape Griffon Gyps coprotheres, with emphasis on the effects of supplementary feeding

Survival rates are crucial demographic parameters for modelling the population dynamics of the Cape Griffon vulture. Previous survival estimates based on ring recoveries are seriously flawed and have been heavily criticized. To provide better estimates, 97 nestlings were individually colour-ringed in the winterrainfall region of South Africa from 1979 to 1987 and an intensive resighting campaign was mounted for 17.5 years (1980 to mid-1997). Although survival rate is known to vary with age, particularly in the first few years of life, this study indicates that it is also a function of calendar year. Supplementary food was provided for the study population from 1984 onwards and there was a concomitant increase in the survival rate of first-year birds. Eighty generalized linear models were built to estimate survival rate as a function of age, calendar year, cohort and supplementary feeding. First-year survival rate was estimated as 42.3% per annum (95% limits: 29–56%), increasing to 68.9% (54–81%) after the introduction of supplementary feeding. Age-specific survival rates were 88.8% per annum (77–95%) in the second year, 78.7% (64–88%) in the third year and 67.6% (58–76%) for birds aged four years or more. Our survival estimates are higher than previous values and have greater reliability because they are based on direct observations of known-age birds. The loss of colourrings is a serious impediment to estimating survival among older birds and the technique described here was not used to estimate adult survival.

What Selective Pressures Have Driven the Evolution of Deferred Northward Migration by Juvenile Waders?

Deferred northward migration by young waders has been ascribed to the of long-distance migration, but the nature of these risks has not been explored. We suggest that the low foraging proficiency of young waders is an important factor in the evolution of deferred migration by some small to mediumsized waders. Because of the disparity between adult and juvenile energy intake rates, juveniles would be prevented from migrating synchronously with adults if their migration involved one or more refuelling stops. The slower migration of juveniles would result in their late arrival at the breeding grounds, with a concomitantly high risk of breeding failure. The longer the migration and the higher the breeding latitude, the greater this risk, conforming with the conclusion of Summers et al. (1995) that young waders overwintering close to the breeding grounds are more likely to migrate north than are young waders which overwinter further south. We further suggest that the probability of successful breeding by late arriving long-distance migrants is so low that the risk of first-year birds dying on northward migration does not have to be high for the behaviour to be selected against and thus be lost from the population.

Migratory movements of western European Montagu's Harrier Circus pygargus: a review

We review the migratory movements of European Montagu's Harriers, based on 152 ringing recoveries (from data published up to 1993) and published data on counts at migratory convergence points. Data were analysed according to age groups and time of the year (pre- and post-breeding migration). Results showed two main migratory routes across the Mediterranean for the western European Montagu's Harriers (Gibraltar and the Sicily Channel). Passage frequency was higher in the post-breeding than the pre-breeding migration in the Gibraltar Strait, but the opposite occurred in the Sicily Channel. We discuss the possibility that Montagu's Harriers present a partially circular migration, maybe as a result of movements within the wintering areas. Recovery frequency varied according to age group, being lower for first-year birds than expected from random, which suggests that some first-year birds do not return to the breeding areas during their first summer.

Migration and moult of Dunlin Calidris alpina wintering in the central Mediterranean

Dunlin migration in northeast Italy is described. An attempt to identify the main routes and staging areas used by birds wintering in the central Mediterranean is presented. The results of monthly counts from 1990–1995 revealed that the bulk of the population occupied the wintering area in October and left for the breeding grounds in April and May. The analysis of 342 Italian recoveries of foreign ringed birds showed that 65% were ringed during post-breeding migration through the Baltic Sea, whereas just a few birds had been ringed in western Europe. First-year birds arrived in autumn with a single migratory wave, peaking in October. Two categories of adults were identified during post-breeding migration: birds which directly reached Italian wintering sites and birds which arrived after they had suspended their migration for moulting: the Azov/Black Sea wetlands are suggested as possible moulting areas. Out of 2444 adults and 1627 first-years ringed between 1989 and 1996 at our study area, we obtained a total of 42 recoveries abroad and evidence of direct links between Azov/Black Sea and N Adriatic wetlands, both during autumn and spring migrations. Primary moult was observed only in adults arriving early, the second migratory wave being composed of moulted birds. Locally moulting adults adopted a moult strategy characterized by high raggedness scores, typical of resident moulters. Body mass was not affected by primary moult stage or intensity, winter mass values being reached two weeks after the average date of primary moult completion.

Interseasonal Changes in Shorebird Habitat Specialisation in Moreton Bay, Australia

SummaryHabitat use by shorebirds in Moreton Bay was examined by monitoring 56 intertidal study sites during southward and northward migrations between 1988 and 1990. Sites were selected to include four areas in Moreton Bay that had distinct intertidal habitats (mainland, island, coral and sewage habitats). At each site, the relative abundance of species was recorded and habitat assessed using sediment particle size analysis and visual assessment of sea-grass coverage. Spatial and temporal patterns of habitat use were characterised by variation in the relative abundance of species in habitats. Spatial and temporal patterns were integrated by seeking patterns that could explain the variability in community structure between different times of year, and that could be attributed to temporal aspects of migration. Species diversity and measures of habitat specialisation supported the prediction that shorebirds are more concentrated within preferred habitat during the northward compared with the southward migration in Moreton Bay, and that the size of this change is related to the respective degree of specialisation of each species. The change between seasons may have been caused either by greater energy reserves of individual birds at the time of northward migration or an increase in the ability of first-year birds to locate suitable habitat by this time of year. The protection of all habitats in Moreton Bay is required to conserve the full range of shore-bird species using both the eastern and western portions of the Bay.

Organochlorine and heavy metal residues in breast muscle of known-age thick-milled murres (Uria lomvia) from the Canadian Arctic.

Thick-billed murres (Uria lomvia) originating from breeding colonies in the Canadian Arctic were collected on their wintering grounds off the coast of Newfoundland. Murres had been previously banded such that the age of each bird could be determined upon collection. This allowed us to explore the possible relationships between age and contaminant levels in the thick-billed murre. Samples of breast muscle were analyzed for organochlorines (chlorobenzenes, hexachlorocyclohexanes, DDTs, chlordanes, mirex, dieldrin, and PCBs) and metals (selenium, cadmium, mercury, and lead). Levels of both organochlorine and metal residues were sufficiently low so that toxic effects were unlikely. First-year birds contained lower levels of DDTs, mirex, dieldrin, and PCBs compared with older birds, reflecting lower levels of contamination of these compounds in food chains at breeding colonies located at higher latitudes. Higher levels of chemical residues in older birds may reflect greater direct input of those organochlorines into the wintering grounds via the highly contaminated St. Lawrence River. Levels of chlorobenzenes, hexachlorocyclohexanes, and chlordanes, which reflect atmospheric deposition, were not detected at higher levels in older birds. Of the metals, only cadmium was detected at higher levels in older birds.

Seasonal distribution and timing of migration of Cormorants Phalacrocorax carbo sinensis breeding in Denmark

The recent expansion of the Cormorant Phalacrocorax carbo population in Europe has led to management conflict throughout Europe, increasing the relevance of describing the migration pattern of each country's breeding population. We use 2279 recoveries and 16 769 resightings of 4735 colour-ringed individuals to describe dispersal and timing of movements of Danish Cormorants. Most Cormorants dispersed from the colonies to coastal areas and freshwater lakes in Denmark, Sweden and northern Germany in July. Southward movements took place throughout July to December. Major departure from the post-breeding areas occurred from August to mid-October, with many birds staging at Dutch and Alpine lakes between September and October, and with arrival in the Mediterranean mainly from October to November. Spring migration was fast, occurring from mid-February to March. First-year birds migrated south faster and reached the wintering areas sooner than adults, but left these later and moved north more slowly than adults. Wintering occurred from Portugal in the west to Greece in the east, and from Denmark in the north to North Africa in the south. The majority of Cormorants spent the winter in Mediterranean France, Italy, Yugoslavia, Albania, Algeria and in particular in Tunisia. Adult males stayed closer to the breeding areas in winter than females, and adults tended to winter further north than first-year birds. Sex differences in body size and advantages of arriving early at the breeding sites may explain why males wintered further north than females.

Autumn migration of Blue Tit Parus caeruleus at Falsterbo, Sweden 1980–94: population changes, migration patterns and recovery analysis

Extensive ringing data from Falsterbo, South Sweden, were used to analyse numbers, migration patterns and recoveries in the Blue Tit Pants caeruleus during 15 years (1980–94). The ringing totals as well as the totals from the migration counts at Falsterbo showed an overall increase of Blue Tits during this period. This corresponded with the trends from other monitoring projects in Sweden as well as the number of annually ringed nestlings. Analyses of the daily and seasonal migration patterns and the age and sex composition were carried out. The majority of the migrating Blue Tits were females, but with an increasing proportion of males with increasing numbers of migrating Blue Tits. The majority of the migrating Blue Tits were first-year birds and this proportion increased with the strength of migration. The results indicated that the same individuals may show repeated migration during several seasons, more like regular migrants than true irruptive species. The recovery analysis shows breeding area, migration routes and wintering areas for Blue Tits ringed or recaptured at Falsterbo. Obviously the major part of the birds originate from southern Sweden. They are short-distance migrants wintering in Denmark and northern Germany. Many Blue Tits also return inland when confronted with the sea at Falsterbo. The intensity of migration varied a lot from year to year. Strong migratory movements occurred more often towards the end of the study period and with increasing numbers of Blue Tits involved. It appeared that the key factors for the occurrence of strong migratory movements were a high population density, caused by high winter survival and good breeding results, in combination with a low amount of Beech mast or other food resources during the following autumn.

Seasonal patterns of abundance of Kelp Gulls Larus dominicanus at breeding and non-breeding localities in southern Africa

Crawford, R.J.M., Nel, D.C, Williams, A.J. & Scott, A. 1997. Seasonal patterns of abundance of Kelp Gulls Larus dominicanus at breeding and non-breeding localities in southern Africa. Ostrich 68 (1): 37–41. At Malgas Island, Western Cape Province, South Africa, active nest sites of Kelp Gulls were recorded from August to February, but mainly between October and December with a peak in November. In August and September all active sites were recently-made scrapes without eggs or chicks. Eggs were found from early October until January and chicks from late October to early February. At Dassen Island, Western Cape Province, numbers of adult Kelp Gulls are highest during the main October-December breeding season. After breeding, adults disperse from the island, with only 4% remaining by May. First-year birds were observed at Dassen Island from February to July, with mean numbers decreasing after April. At De Hoop, Western Cape Province, numbers of Kelp Gulls were also highest during the breeding season, but the decrease in the non-breeding season was less marked. Near Walvis Bay, central Namibia, at a non-breeding site, numbers of Kelp Gulls were highest outside the breeding season, indicating dispersal of birds away from colonies after completion of breeding.

Local Survival of Dunlin Wintering in California

We estimated local annual survival of 1,051 individually color-banded Dunlin (Calidris alpina) at Bolinas Lagoon, California from 1979 to 1992. Resighting rates for birds banded as adults varied significantly among years, and resighting rates for first-year birds varied by sex and year. No significant differences in local survival rates were found between males and females in any age classes. First-year birds had lower local survival rates than adults. We suspect that raptor predation accounted for much of this difference and other variation in survival rates. Adult Dunlin had lower local survival rates in the year of capture than in subsequent years. Variation in resighting of some groups of individuals including transient Dunlin may account for some differences. However, capture and release of Dunlin may induce short-term behavioral changes that increase the risk of depredation by avian predators within the first few days after capture.