0000000000024790
AUTHOR
Aivars Mednis
Sources of variation in survival and breeding site fidelity in three species of European ducks
Summary 1 We used long-term capture–recapture–recovery data and a modelling approach developed by Burnham (1993) to test a priori predictions about sources of variation in annual survival rates and fidelity within a population of individually marked females in three species of European ducks from a breeding ground study site in Latvia. 2 True annual survival was higher for diving ducks (tufted duck 0·72, common pochard 0·65) and lower for northern shoveler (0·52). Survival of female diving ducks was positively correlated with mean winter temperatures at Western European wintering areas, the relationship being much stronger for pochard. 3 We present the first unbiased estimates of breedin…
Changes in the Breeding Bird Fauna, Waterbird Populations in Particular, on Lake Engure (Latvia) over the Last 50 Years
The nesting bird fauna (186 species) of Lake Engure and its surroundings has changed considerably over the last 50 years: 18 species have appeared as newcomers (among them 56% of southern, 6% of northern origin), 10 species have ceased nesting (among them 60% of northern, 10% of southern origin). These changes might be explained by global warming. Dramatic changes recorded in all waders can be accounted for by the local habitat loss and a general decline in wider geographic ranges. The Black-headed Gull (Larus ridibundus) population increased from 200 pairs in 1940s to 34,000 pairs in 1986, and then declined to 4,200 pairs in 2002. Nesting duck (all species combined) numbers and their nesti…
MIGRATION AND DISPERSION OF LATVIAN DUCKS
RESUME Le present document traite de la distribution saisonniere et geographique des canards colverts, des canards souchets, des sarcelles d'ete, des fuligules milouins et des fuligules morillons, bagues en Lettonie comme canetons d'un jour ou comme femelles couveuses. Au cours de leurs migrations saisonnieres et de l'hivernage, les colverts ont ete repris principalement en Pologne, Danemark, Allemagne, Pays-Bas, et dans le nord de la France. Les souchets ont ete principalement signales dans le nord de l'Allemagne, au Danemark, aux Pays- Bas, en France, dans les Iles Britanniques et en Espagne; les sarcelles d'ete en Ukraine, Pologne et Italie (seulement deux reprises provenaient des aires …
The occurrence of runt eggs in waterfowl clutches
Abstract Eggs that are abnormally small are called runt eggs, and they occur in clutches across a wide variety of bird species. We surveyed waterfowl researchers to determine the natural frequency of occurrence of runt eggs in wild nesting ducks, geese, and swans. Of 551,632 eggs examined, 215 were runts, yielding a frequency of 0.039%. They occurred at about four times this frequency (0.156% in 21,832 eggs) in a museum oological collection. Runt eggs were not significantly more common within any taxonomic group among wild waterfowl, and their occurrence was not related to the mean clutch size of a species or to whether waterfowl exhibited regular conspecific nest parasitism. Cavity-nesting…
Factors affecting breeding dispersal of European ducks on Engure Marsh, Latvia
Summary 1 We used up to 35 years of capture–recapture data from nearly 3300 individual female ducks nesting on Engure Marsh, Latvia, and multistate modelling to test predictions about the influence of environmental, habitat and management factors on breeding dispersal probability within the marsh. 2 Analyses based on observed dispersal distances of common pochards and tufted ducks provided no evidence that breeding success in year t influenced dispersal distance between t and t+ 1. 3 Breeding dispersal distances (year t to t+ 1) of pochards and tufted ducks were associated with a delay in relative nest initiation dates in year t+ 1. The delay was greater for pochards (c. 4 days) than for tu…
Estimating natal dispersal movement rates of female European ducks with multistate modelling
Summary 1 We used up to 34 years of capture–recapture data from about 22 100 new releases of day-old female ducklings and multistate modelling to test predictions about the influence of environmental, habitat and management factors on natal dispersal probability of three species of ducks within the Engure Marsh, Latvia. 2 The mean natal dispersal distances were very similar (c. 0·6–0·7 km) for all three species and were on average 2·7 times greater than breeding dispersal distances recorded within the same study system. 3 We were unable to confirm the kinship hypothesis and found no evidence that young first-nesting females nested closer to their relatives (either mother or sister) than to …
Effect of Incubation Body Mass on Reproductive Success and Survival of Two European Diving Ducks: A Test of the Nutrient Limitation Hypothesis
The nutrient limitation hypothesis postulates that variation in nutrient reserves during egg laying and incubation are important predictors of future reproductive success of female waterfowl. We tested one component of this hypothesis in two European diving ducks, Common Pochard (Aythya ferina) and Tufted Duck (Aythya fuligula), relating body masses of incubating females to subsequent nest success, and to duckling and adult survival. We based our analyses on 3,224 Common Pochards and 1,812 Tufted Ducks captured and weighed during the last two weeks before ducklings hatched at Engure Marsh, Latvia, in 1978-1993. Adult (ASY) females from successful nests weighed significantly more than those …
RESULTS OF RADIO—TRACKING OF DUCKS IN THE LAKE ENGURE IN SUMMER 1997
ABSTRACT In summer 1997 a project of duck research using radio—telemetry was carried out on the Lake Engure, Latvia. 10 females of Mallards, 10 females of Shovelers, 9 females of Pochards and 6 females of Tufted Ducks were radio—tracked during the period from the hatching of their ducklings till fledging. Information about effect of the harness-type radio-transmitters on different species of ducks has been collected. For 15 ducks home range sizes and distances between nests and range locations were calculated. Mallards used to move further from their nest sites; one Mallard brood after one week spent near the nest site dislocated 8 km to the Southern part of the lake during one day. Problem…