Annual Breeding Success Research Articles

Breeding success and survival in the common swift Apus apus: a long‐term study on the effects of weather

In an analysis of data collected between 1954 and 1993, the breeding success of swifts Apus apus was found to have been positively related to temperatures in June, especially in recent years. Adult survival until the next breeding season, by contrast, was found to have been more vulnerable to low temperatures in July, at the end of the breeding season. In addition to the effects of changes in June and July temperatures, both breeding success and survival have shown further long‐term trends, increasing and then decreasing through the study period. A simulation integrating all these effects suggests that lifetime reproductive success (LRS) in influenced more by changes in lifespan than annual breeding success, and so fluctutations in July temperatures, but not June temperatures, would have important effects.

The Contribution of Some Recent Research on Birds to Ecological Understanding

In this address I discuss the contribution to ecological understanding of four aspects of ornithological research, based on long-term or large-scale studies. Long-term population studies of birds, involving marked individuals, have provided, for more than 20 species, information on lifetime reproductive success (LRS) ; that is, the total numbers of young raised by individuals during their entire lives. LRS values are useful because they combine two key measures of performance (annual survival and annual breeding success) into a single overall measure, which could give a close approximation to Darwinian fitness. In any one bird population, LRS values have proved to be markedly skewed, with most individuals in a generation producing no young and a few producing many young. Depending on species, some 3-9% of fledglings in one generation produced half the young in the next generation. The application of island biogeography and metapopulation theory to the bird populations of woods and other fragmented habitats has confirmed the widespread occurrence of the species-area relationship, and the importance of the stochastic processes of local extinction and recolonization in influencing species numbers and distributions among fragments. Certain bird species are found only in habitat patches that are two or more orders of magnitude larger than their individual area needs, as judged from territory sizes. By implication, the more that habitats are fragmented, the more likely are species with special habitat or area needs to disappear, and the more the long-term persistence of the remaining avifauna depends on chance processes. If these points hold for birds, which are among the most mobile of organisms, they surely apply to other less mobile taxa. The nation-wide monitoring of bird populations has revealed long-term declines in many bird species in Britain, associated with modern land-use practices. Research on birds has been paramount in revealing pesticide impacts on non-target species. Some bird populations have been affected directly by pesticides reducing their individual reproductive or survival rates, while others have been affected indirectly by pesticides reducing the abundance of their food organisms, plant or animal. Migration is perhaps more developed in birds than in any other animals. It is impressive in terms of the global scale over which it occurs, the distances travelled, the large proportion of species involved, and the enormous numbers of individual participants. It results each year in huge seasonal changes in the distribution of birds over the earth's surface, linked to seasonal changes in food supplies. In some bird species, annual changes in overall population levels were related to conditions on the wintering range, and in other species to conditions on the breeding range. Large-scale migration studies have raised questions on the factors influencing the geographical ranges of birds, and on the relationship between breeding and wintering areas, and between abundance and distribution.

Influence of Body Condition on Reproductive Decision and Reproductive Success in the Blue Petrel

Following the prediction that body condition affects whether eggs are laid in birds, we examined variations in prebreeding body condition (i.e. body mass one month before laying, adjusted for structural size, breeding experience, and date of return), incidence of breeding, and reproductive success of male and female Blue Petrels (Halobaena caerulea). Condition was inversely correlated with date of return and positively related to breeding experience in males, but not in females. In both sexes, condition displayed year-to-year variations; the 1991-1992 season was distinguished by poor condition, low incidence of breeding, and low reproductive success. Condition in both males and females, and breeding experience in males had significant effects on the to breed. Breeding experience also influenced the decision to breed, especially in males. Condition, but not breeding ex- perience, had a significant influence on male incubation success. Female breeding perfor- mances were not related to condition but to breeding experience. Annual average breeding success was highly variable and significantly correlated with male condition. Prebreeding visits appeared to be critical for this pelagic seabird and may allow individuals, through their condition, to manage their reproductive investment. We suggest that condition mainly affects egg formation in females and, together with breeding experience, influences the duration and the quality of prebreeding colony attendance in males. The potential relationships of body condition, breeding experience, reproductive investment, and future survival are dis- cussed. Received 11 November 1993, accepted 25 February 1994.

A comparison of breeding success and prey of the Common BuzzardButeo buteoin two areas of northern Scotland

The breeding success of 2 Common Buzzard Buteo buteo populations in the north of Scotland, were studied over the period 1977–¸89. Marked differences were found in breeding density, clutch size and nesting success. An examination of prey remains found at nests in the 2 areas provided a possible explanation. The more successful population in Moray were feeding on large prey items such as Rabbits and Wood Pigeons, whereas the other population in Glen Urquhart, fed more on voles and small passerine birds. A parallel study on Tawny Owls in Glen Urquhart showed a strong correlation between their annual breeding success and that of the local buzzards. This fluctuated on a 4- year cycle and was probably in response to vole abundance.

Patterns of adoption in ring-billed gulls: who is really winning the inter-generational conflict?

Although at variance with Darwinian theory, adoption of unrelated offspring has been reported in a variety of ground-nesting colonial seabirds. Pierotti & Murphy (1987,Anim. Behav.,35,435-444) suggest that an inter-generational conflict exists between disadvantaged chicks and unrelated adults, a conflict that often results in wandering chicks successfully soliciting investment from foster parents. Of 47 ring-billed gull,Larus delawarensis, chicks that departed their natal broods over four summers of field work, 34 remained in recipient broods for 3 or more days and received parental care (i.e. were successfully adopted), and 13 remained in recipient broods for less than 3 days (‘runners’). Chicks in broods that were subsequently subject to abandonment were fed at a significantly lower rate (on a per chick basis) than chicks in control broods (which neither adopted nor had a chick depart) or broods that subsequently adopted a chick. In most cases, adoptees were older than the oldest resident chick in the accepting brood, but runners were younger than resident chicks. Pairs whose oldest chick was less than 7 days were more likely to adopt foreign offspring than pairs with older chicks. Twenty-six (76%) of the 34 adopted chicks survived to at least 24 days (fledged). Pairs that adopted a chick realized a lower annual breeding success (chicks fledged/pair) than control pairs or pairs that had a chick depart their brood. Disadvantaged chicks that gain permanent acceptance into foreign broods ‘win’ the inter-generational conflict at the expense of the foster parents.

THE INFLUENCE OF THE ENVIRONMENT ON BREEDING SUCCESS OF A SUBURBAN POPULATION OF CRESTED BARBETSTRACHYPHONUS VAILLANTII

Summary Van Zyl, A.J. 1994. The influence of the environment on the breeding success of a suburban population of Crested Barbets Trachyphonus vaillantii. Ostrich 65: 291–296. I studied the breeding biology of the Crested Barbet Trachyphonus vaillantii in Colbyn, a suburb east of Pretoria, South Africa, for nine breeding seasons from 1981 to 1989 to examine patterns in annual breeding success, breeding attempt success in multiple broods, and rainfall. The modal incubation period was 14 days and the nestling period ranged from 28 to 31 days. Average clutch size for all the years was 3,3 eggs/clutch and there was no significant difference in clutch size or number of young fledged/nest between years. On average, Crested Barbet pairs made 2,4 breeding attempts/season. There was no difference in clutch size or breeding success between the breeding attempts. Crested Barbets nesting in natural nests laid on average larger clutches than those in artificial nestboxes, but had non-signficantly lower breeding success...

High annual variability in reproductive success and survival of an Antarctic seabird, the snow petrel Pagodroma nivea : A 27-year study.

Demographic parameters were estimated for snow petrels Pagodroma nivea nesting at Pointe Géologie Archipelago, Adélie Land, Antarctica between 1963 and 1990; 21 years of data on adult survival and 27 years of data on breeding success are available. The average age of first return and first breeding were 8.1 and 9.9 years respectively and there was no signifcant difference between the sexes. The overall breeding success averaged 51.3% and was very variable between years (21-80%). Breeding failure was mostly due to incubation failure and annual breeding success was negatively correlated with average snow falls in October-November and October-March. Breeding frequency was very low, averaging 52% of seasons during a reproductive lifetime. Good quality sites, with high occupancy rate and high breeding success were few in the study plots. Poor years in 1966-1967, 1976-1977 and 1983-1984, with low breeding success, very low proportions of nets with breeding attempts and high numbers of non-breeders, occurred 1 year after large-scale El Niño Southern Oscillation (ENSO) events. Snow petrels exhibited very low philopatry. Only 45 birds have been recovered in the study plots from a total of 1115 banded fledglings giving an estimated rate of return of 12.9% between fledging and 3 years old. Annual survival between 3 and 10 years was 91.4%. Annual adult survival (93.4%), though variable, was low during poor years of 1977-1978 and 1983-1984. Adult survival of males (94.7%) was not significantly different from that of females (93.9%). Over the study period, the population of Pointe Géologie was stable. Using the estimated parameters, a Leslie model gave a growth rate of 0.948%, which was probably compensated by immigration (5.7% per year). Restricted numbers of good-quality sites at the place of birth could have led young birds to prospect other colonies and could have selected low philopatry. High adult survival, strong site tenacity and capacity to spread breeding over a long lifetime are probably part of the adaptive strategy of this small fulmarine petrel facing highly variable environmental conditions.

Influence of weather conditions on pallid swift Apus pallidus breeding success

The reproductive ecology of three colonies of pallid swift in a warm continental climate (Piedmont, NW‐Italy) was studied over a ten years period About 60% of the clutches were laid in late May and June, but continued until late August and September, when some females laid a second clutch Clutch size and the mean number of fledged young decreased progressively from spring to autumnLaying dates were influenced by rain and temperature unfavourable weather conditions during May induced most females to postpone egg laying until June Clutch size was not related to the rain or temperature parameters consideredThese observations differ from the findings about the common swift studied in cool temperate areas, where a very short stay in the breeding colonies does not allow a delay in laying, and spring weather conditions therefore have a strong influence on clutch size There are also differences about the effect of weather on chick rearing In warmer climates, typical of our colonies, fledging success is hindered both by too dry or too rainy seasons, even if these situations very rarely occur and the three‐egg clutch is always the most productive In colder climates the breeding success of the common swift depends primarily on the climatic conditions of May. and in bad weather a two‐egg clutch is more productive than a clutch of three In summary, the annual breeding success of the pallid swift appears little influenced by weather changes, due to a lesser impact of adverse conditions in Southern climates and the possibility, for this species, of shifting the laying period in response to a temporary worsening of climatic conditions

Use of Social Indices to Predict Reproductive Success in Canvasbacks

We correlated temporal changes in social groupings of canvasbacks (Aythya valisineria) breeding near Minnedosa, Manitoba, with an independent estimate of hen success during 1974-80. Roadside counts of pairs, lone males, and flocked males were made along transects at 5-day intervals, normalized to percentages to allow comparisons among years, and plotted to obtain measurements of selected areas between and under the curves. An estimate of hen success was regressed on these selected graph areas each year to derive a predictive equation. Graph areas (social indices) determined from temporal changes in the proportion of pairs, lone males, and flocked males correlated (r2 = 0.69-0.93) with hen success. This technique avoids the need for pair counts, nest searches, and brood counts and provides managers with a useful index to evaluate local management practices and to predict yearly production in time for setting hunting regulations. J. WILDL. MANAGE. 54(1):66-72 With onset of egg laying and incubation, female ducks become less visible, and observed social groups change from predominantly paired males and females to mostly lone and flocked males (Dzubin 1969). LeBret (1961) found that hatching dates of mallards (Anas platyrhynchos) could be calculated from the time pairs began to break up and lone males first began to appear. Dzubin (1969) found that when lone male mallards first comprised over 10% of pairs, females were beginning egg laying, and the first appearance of 2-3 males in a group indicated the start of incubation. Olson (1964) reported that canvasback sex ratios in early June provided a useful index to ensuing production. Therefore, if we assume observed males to be paired with nesting females and if there is minimal immigration or emigration in the local population, then seasonal changes in observed social structure of the population should be related to some measure of female reproductive success. Traditional methods of estimating reproductive success in ducks require detailed information on the size of the breeding population and the number of young produced for any given area. However, in addition to being time conI Present address: U.S. Fish and Wildlife Service, Office of Migratory Bird Management, Laurel, MD 20708. This content downloaded from 157.55.39.84 on Tue, 07 Jun 2016 05:24:06 UTC All use subject to http://about.jstor.org/terms J. Wildl. Manage. 54(1):1990 CANVASBACK BREEDING INDEX * Serie and Cowardin 67 suming and labor intensive, these methods must overcome a wide spectrum of potential biases, such as weather, breeding phenology, bird mobility, behavior, and changing observation rates based on vegetative growth (Diem and Lu 1960, Dzubin 1969, Sauder et al. 1971, Sorenson 1978, Sugden and Butler 1980). Alternative methods depend on use of radios (Cowardin et al. 1985) and marking techniques (Trauger 1971) to track individual females and assess reproductive success, but they are also subject to bias (e.g., radio malfunction, marker loss, and behavior modification). In spite of these special problems, accurate estimates of annual productivity are integral to the management of continental duck populations and are necessary to formulate harvest strategies. Therefore, development of new, more rapid, and reliable methods of indexing annual breeding success are needed for setting annual hunting regulations and assessing management practices on local areas. We described temporal changes in social groups of canvasbacks during the breeding period and investigated the potential for using social indices to predict reproductive success. This method of indexing productivity was first described by J. R. Serie (J. R. Serie, 15th Semin. Breeding Biol. of Waterfowl, Delta Waterfowl and Wetland Res. Stn., Manitoba, 1980) and was later adapted and modified by Hochbaum et al. (1987). J. H. Stoudt initially established roadside transects near Minnedosa, Manitoba, and we thank D. L. Trauger for his encouragement to periodically record canvasback social groups. Field assistance was provided by L. Deede, H. A. Doty, T. Fondell, T. Jessicoff, D. H. Johnson, J. H. Noyes, F. Roetker, and L. Vanderholf. We are grateful to M. G. Anderson and the Delta Waterfowl and Wetlands Research Station for their assistance. In particular, we are indebted to T. L. Shaffer for statistical analyses. We thank T. G. Hanson for typing the manuscript and J. E. Austin, G. S. Hochbaum, C. E. Korschgen, R. B. Oetting, A. B. Sargeant, and T. L. Shaffer for review of manuscript drafts.

A multifactorial explanation for variation in breeding performance of Brent Geese Branta bernicla

The dramatic differences in annual breeding success of Dark‐bellied Brent Geese Branta b. bernicla are generally interpreted as being caused by variable conditions on the arctic breeding grounds. The recently revived discussion on this issue mentions, in particular, the cyclic variation in abundance of lemmings, resulting in cyclic variation of predation pressure on bird nests by arctic foxes, as the main factor determining whether Brent Geese are able to breed successfully or not. New data on the spring condition of Brent Geese in Western Europe and wind conditions during migration from the spring staging areas to the breeding grounds show that these factors also influence breeding output.

Natural Selection, the Costs of Reproduction, and a Refinement of Lack's Principle

Natural Selection, the Costs of Reproduction, and a Refinement of Lack's Principle

THE BREEDING OF SOME S.W. ECUADORIAN BIRDS

SUMMARYThe breeding of about 40 species of birds in the Ancon district of the Guayas Province of S.W. Ecuador is described. The information is based on the records of about 2000 nests observed during 1955–1958. About half the species are birds which range over much of Central and South America and whose breeding has been previously described, though usually casually. For these my own remarks are confined to new information, doubtful points and confirmatory details. The rest are species more or less confined to the west coast of South America between Ecuador and Chile, and for which there is either little or no breeding information in the literature. These are treated under headings of nest site, nest, eggs, clutch‐size, laying, incubation, nestling period, breeding success and season, with general remarks where appropriate. For most species, closely determined incubation and nestling periods arc given, and for some, quantitative data on clutch‐size and breeding success are available. In some species differences have been found for annual mean clutch‐size, mean clutch‐size laid before and after rain, annual breeding success and fledging success, doubtless due to pronounced climatic variation from year to year which either has a direct effect or influences predation.These matters are discussed generally in the introduction, with particular mention of 10‐day incubation periods, the rapid nesting cycle of several finches, precociousness of their young, and comparison of breeding success with that of European species, as well as the peculiar ecological variations of the district and changes in predators.In the sequel the statistical aspect of my data is analysed by Dr. Monte Lloyd and I have followed this with somea posterioriremarks.

THE COMPOSITION OF GOOSE POPULATIONS

Summary.Detailed knowledge of changes in the size and composition of goose populations is of importance in conservation. Long‐term inventories of goose numbers have so far been made only in the United States of America. American and European studies of movement, and of survival, have chiefly depended on the recovery of ringed geese. It has slowly been realised that direct observations of goose flocks can provide much of the information needed to determine the age‐structure of flocks, annual breeding success and mortality. Studies of goose populations employing all the available techniques are now being actively pursued in Britain as well as North America. Some examples are briefly discussed.