Brood rearing costs affect future reproduction in the precocial common goldeneye Bucephala clangula

Life-history theory assumes a trade-off between current reproductive effort and future reproductive success. There are a large number of studies demonstrating reproductive trade-offs in different animal taxa, particularly in birds. Most bird studies have focused on the costs of chick rearing in altricial species. These costs have been assumed to be low in precocial species, but this aspect has been little studied. We used long-term individual reproductive data from the common goldeneye Bucephala clangula , an iteroparous precocial duck with uniparental female care, to examine whether brood rearing carries costs that affect future reproductive performance. All females were experienced breeders, and possible differences in female quality were ruled out. We compared within-individual (between-year) changes in clutch size, hatching date and body mass between females that had reared a brood in the previous year and females that had not. It turned out that brood rearing involved a cost in terms of clutch size and hatching date the next year, but not in terms of body mass: females that had reared a brood in the previous year laid relatively smaller clutches and laid relatively later than females that had not reared a brood. Our results show that normal brood rearing in a precocial species involves costs that affect future reproduction.     

Movements and mortality of common goldeneye Bucephala clangula broods in a patchy environment

We tested the effect of timing and intensity of deer browsing on compensatory response by willow grown for bioenergy. Browsing was simulated several times during summer and once during winter. The clipping was done at different intensities during the first year after establishment in a new willow plantation, and during the first year after harvest in an older willow coppice. Total aboveground biomass and biomass available for deer browsing were recorded both at the end of the first and the second growing periods after clipping. Both in the new plantation and in the older coppice, the willows fully compensated for biomass losses after winter clipping, irrespective of clipping intensity. On the other hand, total biomass production usually decreased after high-intensity summer clipping. Such a seasonal difference may be explained by the nutrition of remaining buds after clipping. In the new willow plantation, total produced biomass after summer clipping still bottomed at about 50% of the level of control stools at the end of the experiment. In the older coppice, usual browsing levels by deer in summer, roughly corresponding to the moderate clipping intensities used in this experiment, did not influence total produced biomass. The newly established willow stools reacted to summer clipping by undercompensating in terms of biomass available for deer browsing, while older stools could overcompensate. Compared to stools clipped in late summer, willow stools clipped during early summer were able to compensate earlier and stronger. The higher the proportion of twig biomass removed by summer clipping, the lower the compensatory growth by willow. Depending on the circumstances, the fast-growing willows responded within the whole continuum from under- to overcompensation, and some implications for the management of willow plantations and large herbivores are discussed.     

Survival of common goldeneye Bucephala clangula ducklings in relation to weather, timing of breeding, brood size, and female condition

The survival of common goldeneye Bucephala clangula ducklings during their first week of life was studied in relation to hatching date, brood size, female condition, and weather (temperature and precipitation) during the first week post-hatch by using data from radio-marked females and their broods. Also, age-specific variation in the survival of the young was determined until fledging (over 50 d of age). Survival was lowest in the first week after hatching. Hatching date, brood size, and first week temperature and precipitation were poor predictors of duckling survival during the first week after nest exodus. Instead, the ducklings of females in a better body condition survived better in their first week of life. The results suggest that weather does not have a direct effect on downy ducklings' survival, but the condition of the female seems to be an important determinant of the survival of common goldeneye ducklings.     

Conspecific nest parasitism is associated with inequality in nest predation risk in the common goldeneye (Bucephala clangula)

Previous studies of the role of nest predation in conspecificnest parasitism have not taken into account the possibilitythat predation risk may not be randomly distributed among nestsites and that breeding individuals may use different cues toassess the risk and adjust their reproductive tactic betweenyears accordingly. Especially in cavity-nesting species, therole of nest predation in conspecific nest parasitism has beendownplayed, while the role of nest site limitation has beenhighlighted. Using both observational and experimental data,I show that in the common goldeneye (Bucephala clangula), acavity-nesting species in which conspecific nest parasitism iscommon, predation risk varies considerably between nest sitesand does not follow a random expectation. The inequality inpredation risk between nest sites also showed up in the occurrenceof parasitized nests in an experimental setup. Nests parasitizedin year t were more frequent in those nest sites that were notdepredated during the previous nesting attempt in year t - nthan in nest sites that were depredated and in control nestsites that had not been used for nesting before. A nest siteaddition experiment revealed that conspecific nest parasitismwas not associated with nest site limitation. My findings givesupport for the hypothesis that nest predation is an importantecological factor explaining conspecific nest parasitism ingoldeneyes.     

Selection of nest sites by a hole-nesting duck, the Goldeneye Bucephala clangula

Nest site preferences were examined for a population of Goldeneye Ducks breeding in nest boxes in Värmland, central Sweden. Some nest boxes were occupied more often than others even if females returning to the same nest box were excluded from the analysis. Nest boxes located higher up trees were occupied more often than those close to the ground and some spatial 'cluster groups' of boxes were occupied more often than others. Otherwise nest site prefernces were not related to any measured physical attributes of the boxes. Prefernces for nest boxes seemed to be based mainly on a tendency for females to select those that had been occupied by other females in the preceding year, especially if they had bred successfully. As a result of this, the occupancy of nest boxes was not random over years but rather progressed in a series of runs; a period of consecutive years in which a box was occupied was followed by a period of years in which it was empty.
There were reproductive consequences for these prefernces in that females occupying preferred boxes were less likely to lose their clutch to a predator. These females also bred earlier in the year and produced larger clutches and broods than females breeding in other boxes.     

Female wing plumage reflects reproductive success in Common Goldeneye Bucephala clangula

Recent studies on the function of female plumage characteristics have yielded ambiguous results. Some studies have found an association between different physiological, ecological or behavioural traits and female plumage, while others have found no association and interpret female plumage as neutral in function. We observed a high variance among females in both wing plumage and breeding success in female Common Goldeneyes Bucephala clangula , a sexually plumage-dimorphic diving duck. We studied the association between female wing plumage and hatching date. Principal component analysis of four wing patch area measurements derived a single factor describing wing plumage. Wing plumage was strongly associated with hatching date, which is the most important determinant of goldeneye recruit production; irrespective of age, females with more white in the wing bred earlier than individuals with more black in the wing. We propose that the wing pattern in Common Goldeneye females reflects individual quality.     

Decline of Canada geese (Branta canadensis) and common goldeneye (Bucephala clangula) associated with a collapse of eelgrass (Zostera marina) in a Nova Scotia estuary

Mean numbers of migrant Canada geese (Branta canadensis) in Antigonish Harbour in the southern Gulf of St. Lawrence (Canada) during October to December were similar (approx. 450–500 birds) for the period 1998–2000. Similarly, during this period, geese used two foraging sites. However, in 2001, the average number of birds decreased by half and the primary foraging sites were used only rarely. This coincided with a decline of about 95% in the biomass of roots and rhizomes of eelgrass (Zostera marina) that occurred between October 2000 and 2001. Eelgrass is the principal food of geese in this estuary. In addition, there was a reduction of around 50% in the numbers of common goldeneye (Bucephala clangula), which feed on invertebrates associated with eelgrass. Lower than usual weekly abundances of geese and goldeneye are probably the result of an unusually short residence time in the estuary, rather than a decline in the total number of visiting migrants. We attribute these changes in the distribution and abundance of geese and goldeneyes to the dramatic decline in eelgrass. Electronic Publication     

Reproductive performance of Common Goldeneye Bucephala clangula females in relation to age and lifespan

We studied the effects of female age and length of lifespan on reproductive performance in the Common Goldeneye Bucephala clangula , a precocial species with self-feeding chicks. Dependent variables studied were the occurrence of failed nesting attempts and non-breeding years, clutch size, nesting and hatching success, female condition and recovery rate of offspring. To avoid misinterpretations resulting from age-dependent quality changes in the cohorts, individuals with different lifespans were separated in the analyses. There was no evidence that females of different lifespan differed in reproductive strategy. The data revealed no significant differences in nest losses, occurrence of non-breeding years, timing of nesting or clutch size, but the physiological condition of short-lived females was poorer than that of longer living females. This accords with the prediction that poor-quality females invest proportionally more in reproduction than high-quality females and consequently die earlier. The most productive individuals were those that lived longest. The only indication of senescence was the low recovery rate of offspring produced by old females. The last breeding attempt did not differ in any observable respect from the penultimate attempt, implying that the last investment in reproduction was no heavier than the previous one.     

Isolation and characterization of 22 polymorphic microsatellite loci for the Barrow's goldeneye (Bucephala islandica)

We describe primers and polymerase chain reaction conditions to amplify 22 microsatellite loci from the Barrow's goldeneye (Bucephala islandica). The primers were tested on 27 individuals from a population breeding in British Columbia, Canada. The developed primer pairs yielded an average of 6.11 alleles per locus (range 2-12), an average observed heterozygosity of 0.70 (range 0.07-0.96) and a polymorphic information content of 0.07-0.88.     

Female Goldeneye Ducks (Bucephala clangula) Do Not Discriminate among Male Precopulatory Display Patterns

Female goldeneyes remain motionless on the surface of the water while single males circle them performing a series of highly stereotyped displays. After performing between eight and 90 of these displays the male either copulates or attempts to copulate with the female. However, females allow only 58% of males to mount them, while rejecting 42%. We have examined 804 of these precopulatory sequences containing 11,841 actions in an effort to determine why females find some display sequences of males unsuitable, while others are accepted. Males have an extraordinarily varied sequence of actions, and sequence variation leading to successful and unsuccessful copulation attempts was similar. Most surprising was the tendency of males to eliminate one of the five actions, whether in successful or unsuccessful attempts. As unlikely as we think it might be as the result of natural selection, the only statistically significant difference we found between successful and unsuccessful attempts was the reduction in the frequency of expression of one or more of the behaviors in successful attempts. These observations, coupled with the large variation seen in most sequences, suggest that there is not a correct sequence, or even a correct set of actions leading to copulation. The male must, however, perform goldeneye species-specific precopulatory behavior as performed by adult males, although it apparently can be performed in a wide variety of patterns.     

Reliability of egg morphology to detect conspecific brood parasitism in goldeneyes Bucephala clangula examined using protein fingerprinting

Eadie (1989) developed a method based on variation between females in egg length, width and weight to detect conspecific brood parasitism in the field: using these three egg measures, Euclidean distance between all pairs of eggs within a clutch is calculated, and if maximum Euclidean distance (MED) between any two eggs exceeds a threshold value the nest is considered parasitized. The MED method has been tested in Finnish and Scottish common goldeneye Bucephala clangula populations but the results have been contradicting. Here we use protein fingerprinting to assess the validity of the MED method. Data comprised 35 clutches of which we knew, based on protein fingerprinting, how many different females laid the clutch (range 1–5 females). The mean MED of non-parasitized clutches (laid by 1 female only) was 1.470 (95% CI: lower 1.169, upper 1.771; n=21) and that of parasitized clutches (laid by 2 or more females) was 3.654 (95% CL: lower 3.083, upper 4.225; n=14). Using a MED>3.0 as a criterion to identify parasitized clutches 89% of all clutches were classified correctly either parasitized or non-parasitized when compared to the identification based on protein fingerprinting. Clutch size and the number of females (beyond 2 females) did not affect the clutch MED, whereas the status of parasitism did. Repeatability of egg length, width and weight were: 0.63, 0.76 and 0.80, respectively, implying that, variation in these egg measures occurs among rather than within females. Our new results confirm that the MED method is reliable enough to detect parasitism in common goldeneye.     

Nesting area fidelity and survival of female Common Goldeneyes Bucephala clangula: are they density‐dependent?

The breeding histories of 218 female Common Goldeneyes Bucephala clangula were recorded between 1971 and 2000 in a study area in Schleswig-Holstein, northern Germany. Females were first recorded breeding at a median age of 2 years usually in their area of hatching (philopatry). One hundred and two of 140 females (73%) re-nested only in one of the 13 nesting areas (clusters of nestboxes) for all their known life of up to 13 breeding seasons. The remaining 38 individuals moved between different nesting areas at least once between breeding attempts. The two oldest females were still breeding at a minimum age of 15 years (i.e. 13 years between first and last recorded breeding attempt). Temporal variations in annual survival rates of adult females could best be explained by a model with annual survival rate varying independently and randomly about a mean of 0.830 (se = ±0.023) with an estimated sd of ±0.092 (95% CI = 0.064, 0.138). No trend in the annual survival rate was detected over the study period of 30 years, although the presence of a moderate trend could not be ruled out. The absence of any discernible trend in survival at a time when the population size increased substantially indicates little, if any, density-dependence in survival of female Goldeneyes during this study.     

Feeding ecology of the diving ducks pochard (Aythya ferina), tufted duck (A. fuligula), scaup (A. mania) and goldeneye (Bucephala clangula) overwintering on Lough Neagh, Northern Ireland

1. The diets of pochard (Aythya ferina), scaup (A. marila) and goldeneye (Bucephala clangula) overwintering on Lough Neagh are dominated by chironomid larvae, while molluscs are more important in that of tufted duck (A. fuligula). 2. Inshore areas of Lough Neagh offer poor feeding conditions for these diving ducks because chironomid larvae and molluscs are of small individual body size or low abundance. These factors lead to all four ducks foraging at least in part at depths greater than those usually exploited. 3. Due to their common consumption of molluscs, the diet of tufted duck shows a higher overlap with that of an introduced roach (Rutilus rutilus) population than with any other duck or fish species. 4. The feeding ecology of tufted duck and roach in Lough Neagh may form an example of distant competition and be at least partly responsible for recent fluctuations in the numbers of tufted duck.     

Aspects of the breeding biology of the Arrowmarked Babbler Turdoides jardineii in South Africa

The breeding success of 18 groups of Arrowmarked Babblers Turdoides jardineii was followed in the 1992–1993 breeding season. The first eggs were laid in late October 1992 and the last eggs in February 1993. Group size was positively correlated with territory size. However, neither group size nor territory size was correlated with the number of offspring raised by a group. Extra adults in a group may not have enhanced the reproductive output of the breeding pair, but they helped in the defence and enlargement of a territory in a saturated habitat.     

Relatedness and spatial proximity as determinants of host–parasite interactions in the brood parasitic Barrow's goldeneye (Bucephala islandica)

Recent studies, which have found evidence for kin-biased egg donation, have sparked interest in re-assessing the parasitic nature of conspecific brood parasitism (CBP). Since host–parasite kinship is essential for mutual benefits to arise from CBP, we explored the role of relatedness in determining the behaviour of conspecific nest parasites and their hosts in nesting female Barrow's goldeneyes ( Bucephala islandica ), a duck in which CBP is common. The results revealed that the amount of parasitism increased with host–parasite relatedness, the effect of which was independent of geographical proximity of host and parasite nests. Proximity per se was also positively associated with the amount of parasitism. Furthermore, while hosts appeared to reduce their clutch size as a response to the presence of parasitic eggs, the magnitude of host clutch reduction also tended to increase with increasing relatedness to the parasite. Hence, our results indicate that both relatedness and spatial proximity are important determinants of CBP, and that host clutch reduction may be an adaptation to nest parasitism, modulated by host–parasite relatedness. Taken together, the results provide a demonstration that relatedness influences host and parasite behaviour in Barrow's goldeneyes, resulting in kin-biased egg donation.     

Aspects of the breeding biology of the Chinspot Batis Batis molitor in Acacia savanna in Swaziland

Some aspects of the breeding ecology of the Chinspot Batis (Batis molitor) were studied in Mlawula Nature Reserve, north-eastern Swaziland. Nests were predominantly built in thorny bushes or trees. Eggs were laid between 20 September and 2 January. However there was a definite peak in November, during which the majority of eggs were laid. Nesting success in the Chinspot Batis was over 30%, while fecundity was 0.65 fledglings/pair/annum. Except for a single occasion, pairs did not double brood unless breeding failed or fledged chicks disappeared. Replacement nests, however, were the norm where a previous nest had failed. Adult batises were observed to feed predominantly on caterpillars and moths. Observations at the nest confirmed that batises fed predominantly moths and caterpillars to their nestlings. The rate at which nestlings were fed depended on their age, older chicks being fed more frequently than younger ones. The correlation between feeding rate and nestling age, and between feeding rate and fledgling age, was significant. In contrast to nestlings, younger fledglings were fed at a higher rate than older ones.     

Aspects of Common Loon (Gavia immer) feeding biology on its breeding ground

Field studies and experiments with hand-reared loons found loons to be facultative predators, foraging on a variety of fishes, crustateans and other aquatic animals. Loons selected certain species and size of prey when present, favoured fusiform shapes and atypical, erratic swimming behavior, but took the most readily available and susceptible to capture, often yellow perch. Chick feeding behaviour developed during the first 8 wks after which physical maturity permitted independent feeding. Juveniles resembled adults in size and shape by wk-11, and were capable of catching all of their own food. Evidence suggests that loons are not harmful to sport fisheries and may ba beneficial by supressing species competing with game fish.Territories averaged 72 ha, and food may be a determinant for maximum size. Based on the average amount of food required by a chick for its first 15 wks (53 kg), plus the daily consumption of older birds (960) g, a pair of loons rearing 2 chicks could remove about 423 kg of food during 5.5 months on territory.     

Aspects of the breeding biology of Dippers Cinclus cinclus in the southern catchment of the River Wye,Wales

Laying dates, clutch and brood size, and the incidence of double brooding, in Dippers breeding in the southern catchment of the Welsh River Wye between 1978 and 1983 are described and compared with data from other regions of Britain and mainland Europe. The mean size of 222 clutches (4.78±0.08) was found to be significantly larger than values given by all other studies in Britain where data were sufficient for statistical comparison. This is discussed in relation to territory quality and other influences.