Changes in adult annual survival rates in a western European population of the White Stork Ciconia ciconia

The population of the White Stork Ciconin ciconia in Alsace (northeastern France) has decreased considerably since 1961. Using recent captureerecapture models, we analysed resighting data on ringed birds resulting from a long-term ringing programme carried out in 1947–1985. Time-dependence and age-dependence in annual survival rates are examined with reference to environmental variables in the Sahel wintering area. Our results show a decrease in adult annual survival rate linked to the severity of the drought in the Sahelian zone.     

Demographic analysis from summaries of an age-structured population

Demographic analyses of age-structured populations typically rely on life history data for individuals, or when individual animals are not identified, on information about the numbers of individuals in each age class through time. While it is usually difficult to determine the age class of a randomly encountered individual, it is often the case that the individual can be readily and reliably assigned to one of a set of age classes. For example, it is often possible to distinguish first-year from older birds. In such cases, the population age structure can be regarded as a latent variable governed by a process prior, and the data as summaries of this latent structure. In this article, we consider the problem of uncovering the latent structure and estimating process parameters from summaries of age class information. We present a demographic analysis for the critically endangered migratory population of whooping cranes (Grus americana), based only on counts of first-year birds and of older birds. We estimate age and year-specific survival rates. We address the controversial issue of whether management action on the breeding grounds has influenced recruitment, relating recruitment rates to the number of seventh-year and older birds, and examining the pattern of variation through time in this rate.     

Breeding site fidelity of blue-winged teal in South Dakota

Assumptions about breeding site fidelity (i.e., fidelity) in blue-winged teal (Spatula discors) are based on limited recapture data and analytic techniques. We banded female blue-winged teal (n = 12,543) from 2003 to 2014 in a 3,800-ha sample area in north-central South Dakota, USA, and used a Bayesian hierarchical modeling approach combining live recapture and dead recovery data to predict probabilities of fidelity, survival, recapture, and reporting. We explored sources of variation including time, annual wet area on the landscape, age, and nest survival, and compared our results to other dabbling ducks that nest in the Prairie Pothole Region, a critically important breeding area for waterfowl in central North America. We found annual estimates of fidelity ranging from 0.20 to 0.91, with mean values of 0.62 and 0.67 for hatch year birds and after hatch year birds, respectively. Our findings indicate that environmental factors may cause blue-winged teal to return to breeding sites more frequently than previously assumed. © The Wildlife Society, 2019     

Longevity and survival of the black stork Ciconia nigra based on ring recoveries

To understand population dynamics, the determination of survival rates is very important. For the black stork Ciconia nigra no survival rate determination has been published to date. This might be due to the fact that ringing activity and recovery numbers in general are still relatively low for the species. The international black stork colour ringing programme is taking place with the participation of 25 countries including Hungary. Altogether more than 7,000 black storks have been colour ringed worldwide, of which 1,069 individuals were marked in Hungary. This article’s objective is the determination of the survival rates for the black stork, as well as to estimate the longevity of the species based on live encounters of ringed individuals. The conclusions are that longevity can be estimated based on the data, and is in agreement with previous knowledge; and that the survival rate of the species, with our present knowledge, shows a significant difference between first year (0.1696, 0.1297–0.219) and older birds (0.838, 0.773–0.887).     

MIGRATION OF THE NORTHWESTERN EUROPEAN POPULATION OF THE CUCKOO CUCULUS CANORUS, AS SHOWN BY RINGING

The migration of the Cuckoo Cuculus canorus is described from recoveries of ringed birds. Young birds begin to migrate in August and most go southwards by September—those in continental Europe move southeast, south or southwest, while those from the British Isles move southeast. In spring, migrants arrive in Europe in April/May, second-(calendar) year birds doing so later than post-second-year birds. In autumn old birds depart in advance of first-year birds; and the individual bird may move stepwise through Europe. Old birds showed a marked tendency to return to the same places inhabited in previous breeding seasons, and birds ringed as nestlings subsequently tended to return to the general vicinity of the natal site.     

Determining the boundaries of migratory bird flyways: a Bayesian model for Eurasian teal Anas crecca in western Europe

Accurate flyway delineation is a prerequisite for effective conservation and management of migratory bird populations, yet such limits have so far mostly been set subjectively. We present a statistical method to infer population boundaries from the analysis of ring recoveries, using a Bayesian framework. The approach was applied to Eurasian teal Anas crecca ringed in Camargue, southern France, and Abberton Reservoir, Essex, eastern England. The results presented show the boundaries of the two teal flyways in western Europe, with a zone of overlap, broadly matching those previously defined. The percentage of teal switching flyways (abmigration rate) was 2.4–2.6%, greater in birds ringed as juveniles than as adults. Abmigrants ended up at sites within the other flyway where the density of local birds was lower than expected by chance, suggesting abmigration resulted from exploratory or aberrant behaviour. The methodology presented here can be used to infer flyway boundaries of any bird with an adequate ring‐re‐encounter dataset, which has crucial consequences for the evaluation of their trends in abundance and hence conservation status, and the management of sustainable harvests.     

Genomic Characterization of H14 Subtype Influenza A Viruses in New World Waterfowl and Experimental Infectivity in Mallards (Anas platyrhynchos)

Recent repeated isolation of H14 hemagglutinin subtype influenza A viruses (IAVs) in the New World waterfowl provides evidence to suggest that host and/or geographic ranges for viruses of this subtype may be expanding. In this study, we used genomic analyses to gain inference on the origin and evolution of H14 viruses in New World waterfowl and conducted an experimental challenge study in mallards (Anas platyrhynchos) to evaluate pathogenicity, viral replication, and transmissibility of a representative viral strain in a natural host species. Genomic characterization of H14 subtype IAVs isolated from New World waterfowl, including three isolates sequenced specifically for this study, revealed high nucleotide identity among individual gene segments (e.g. ≥95% shared identity among H14 HA gene segments). In contrast, lower shared identity was observed among internal gene segments. Furthermore, multiple neuraminidase subtypes were observed for H14 IAVs isolated in the New World. Gene segments of H14 viruses isolated after 2010 shared ancestral genetic lineages with IAVs isolated from wild birds throughout North America. Thus, genomic characterization provided evidence for viral evolution in New World waterfowl through genetic drift and genetic shift since purported introduction from Eurasia. In the challenge study, no clinical disease or lesions were observed among mallards experimentally inoculated with A/blue-winged teal/Texas/AI13-1028/2013(H14N5) or exposed via contact with infected birds. Titers of viral shedding for mallards challenged with the H14N5 IAV were highest at two days post-inoculation (DPI); however shedding was detected up to nine DPI using cloacal swabs. The distribution of viral antigen among mallards infected with H14N5 IAV was largely restricted to enterocytes lining the villi in the lower intestinal tract and in the epithelium of the bursa of Fabricius. Characterization of the infectivity of A/blue-winged teal/Texas/AI13-1028/2013(H14N5) in mallards provides support for similarities in viral replication and shedding as compared to previously described waterfowl-adapted, low pathogenic IAV strains in ducks.     

Changing demography and population decline in the Common Starling Sturnus vulgaris: a multisite approach to Integrated Population Monitoring

Understanding demography is critical for understanding the causes underlying population declines, and for initiating and monitoring policies to reverse them. A method of fitting demographic models directly to avian count data recorded at a sample of census sites is described. The model is applied to national and regional counts of Common Starling Sturnus vulgaris in Britain for the period 1965–2000. Starlings have declined markedly during this time and are now on the list of birds of highest conservation concern. Although there have been small changes in various aspects of breeding success over this time, the analysis shows that these are unlikely to have made much impact on the long-term status of the species. By incorporating estimates of survival, based upon recoveries of ringed birds, the model suggests that the pronounced national decline in Starling numbers since a period of stability in the 1970s is most likely to be due to changes in the survival of first-year birds. This narrows the candidate range of environmental factors which might influence the decline and implicates changes in resource availability.     

Ringing or colour-banding does not increase predation mortality in redshanksTringa totanus

The use of metal and colour‐rings or bands as a means of measuring survival, movements and behaviour in birds is universal and fundamental to testing ecological and evolutionary theories. The practice rests on the largely untested assumption that the rings do not affect survival. However this assumption may not hold for several reasons, for example because the ‘oddity effect’ predicts predators select prey that appear different to their neighbours in order to avoid the ‘confusion effect’. We compared the foraging behaviour and the death rates of redshanks Tringa totanus conspicuously marked with six colour rings and one metal ring each to unmarked birds in a study system, where routinely up to 50% of the total population are killed by avian predators during a winter. If avian predators selectively target and/or have a higher capture success of ringed birds then we would predict the proportion of colour‐ringed birds in the population to decline through a winter. The proportion of colour‐ringed birds in the population did not change over the course of three separate winters, and in one winter the ratio of marked:unmarked birds found killed by sparrowhawks Accipiter nisus was the same as the ratio of marked birds alive in the population. In the year with largest sample size, power was sufficient to detect a greater than 2.2% difference in predation rate between ringed and unringed groups. The average kill rate difference between ringed and unringed birds across the three winters was less than 1% (0.73±2.2%) suggesting that even if there were differences in predation rate that were not detected because of low statistical power they were extremely small. There were no differences in any foraging measures comparing ringed and unringed birds, suggesting that the rings did not affect the ability of birds to meet their daily energy budgets. The results showed that colour‐ringed birds were not preferentially targeted or killed by avian predators, and suggest that the presence of a metal and even several large colour‐rings is unlikely to affect behaviour and predation mortality even under extreme selection.     

A mathematical expectation model for bird navigation based on the clock-and-compass strategy

We present here a mathematical formula for the directional distribution of migratory birds if they use a vector navigation/clock-and-compass strategy to find their winter quarters. It is based on mathematical expectation theory and shows that a simple parabola can describe the expected geographical spread of clock-and-compass birds as a function of migratory distance. Predictions based on this model are then tested against all same autumn ringing recoveries of first-season Pied Flycatchers, Ficedula hypoleuca, ringed in Scandinavia and European Robins, Erithacus rubecula, ringed in Sweden and Finland and recovered north of the Sahara Desert. We find that the predictions of our analytical model fit the ringing recovery distribution of freely migrating conspecifics extremely well.     

No effect of habitat fragmentation on post-fledging, first-year and adult survival in the middle spotted woodpecker

Despite its relevance for the dynamics of populations, the ecological mechanisms underlying juvenile and adult survival are poorly known in most bird species. This study focuses on the effect of habitat fragmentation on early post-fledging, first-year and adult survival of the middle spotted woodpecker Dendrocopus medius by combining data of radio-tagged and ringed birds. Among juveniles, most deaths occurred during the first three weeks after fledging (survival rate: 0.359±0.077) and were mainly caused by predation. After independence, birds faced another critical period during their first autumn-winter that lowered first-year survival further (0.255±0.044), whereas adult mortality was considerably lower (annual survival rate: 0.786±0.074). We did not find any significant effect of habitat fragmentation (measured as patch size and connectivity) on juvenile or adult survival. Sex ratio at fledging did not differ significantly from parity (proportion of females: 0.513) and was not correlated to patch size. Regardless of age, survival did not differ between the sexes, suggesting that a female-biased mortality was not the mechanism behind the presence of unpaired territorial males in this population. Lighter nestlings underwent significantly higher post-fledging mortality, indicating that conditions in the nest may substantially affect survival later in life.     

Interspecific interactions and co-existence in dabbling ducks: observations and an experiment

We studied the possible role of resource limitation and interspecific competition in assemblages of dabbling ducks on breeding lakes in Finland and Sweden with observational and experimental data. After initial vegetation mapping and yearly censuses of ducks in 1985–1990, we collected observational data in 1991–1994 from 28 lakes with natural populations of mallard Anas platyrhynchos and teal A. crecca. Mallard and teal co-occur over vast areas in the Holarctic and they are the only breeding dabbling ducks on many oligotrophic lakes. Both species are migratory in our study regions, teal arriving later in spring than mallards. Log-linear model analysis of observational presence/absence data revealed a positive, not a negative, association between the species. This association was independent of habitat diversity as well as of lake size. Mallard-teal interaction was also studied in a cross-over introduction experiment in 32 other lakes in two years. Wing-clipped mallards were introduced to breeding lakes before the arrival of teal to induce resource limitation and interspecific competition, hypothesized to reduce lake use by teal. The density of mallard pairs on experimental lakes was 2.9–8.0 times higher than on controls, but there was no negative response by teal to the treatment. This is the first combined observational-experimental demonstration of lack of interspecific competition in waterfowl. Our results indicate that heterospecific attraction may affect species co-existence in dabbling ducks. Received: 28 October 1996 / Accepted: 13 January 1997     

Demographic impact of landfill closure on a resident opportunistic gull

The management of mixed municipal waste can have an impact on wildlife and ecosystems. Previous studies have investigated how opportunistic species like gulls can react very fast to new landfills; however, the impact of landfill closure on bird populations is less investigated. Yet, there is a need to understand how fast and to what extent, animal populations can be adapted to new scenarios where the waste will not be deposited in landfill sites anymore. The aim is to determine the influence of landfill closures on apparent survival of a resident Yellow-legged Gull (Larus michahellis) population, used as a model species showing short-distance foraging movements, and with a high dependence on local food subsidies. Complementarily, we built some basic population growth models in order to determine how potential changes in survival (before/after landfill closure) will impact on population growth rate. Using a data set of 4,437 Yellow-legged Gull chicks ringed in four colonies over a period of 13 years, we obtained evidence supporting that the apparent survival was affected by landfill closure, especially if the landfill was located within a buffer of 10 km around the colony. Landfill closure affected the survival of first-year gulls (with a mean decrease of ~ 0.5–0.36), but not of older birds. Consequently, we did not detect a remarkable effect of landfill closures on population growth rate, probably due to the lack of effect on adult survival rates except for one of the surveyed colonies, where we found an annual decline of 7%.     

The survival of understorey birds in the Tropical Rainforest of Ziika,Uganda

Dranzoa, C. 1997. The survival of understorey birds in the Tropical Rainforest of Ziika. Ostrich 68 (2–4): 68–71.

The forests at the shores of Lake Victoria had considerable attention from researchers during the 1970s. Ziika forest is one of the many small forest fragments that fringe the northern part of the lake. This 12 ha forest is surrounded by different habitats, giving it the appearance of a terrestrial ‘island’. Birds were first ringed here from September 1970-July 1972. A follow-up was made in 1988–89, during which 186 birds from 27 different species were ringed. Five years later, survival rates were found to be significantly higher than the expected. Some species appeared to survive better than others. There are various assumptions made in estimating survival rates of understorey birds.     

Survival estimates of Northern Gannets Morus bassanus in Alderney: big data but low confidence

Capsule: There has been a linear increase in the survival rates for both adult and juvenile Northern Gannets Morus bassanus breeding on Alderney in the English Channel. However, given large confidence intervals, improved monitoring is required to better evaluate threats to this population.

Aims: To estimate the age-specific survival and reporting rate from an internationally important population of Northern Gannets M. bassanus breeding at one of the southernmost colonies for this species.

Methods: We use 28 years of ringing and recovery data in order to estimate age-specific survival and reporting rates.

Results: Adult and juvenile survival rates differ, and both survival and reporting rates are considerably lower in first-year birds than older birds. Additionally there is an increasing linear trend in survival rates over time, and a decreasing trend in reporting rates.

Conclusion: Threats to Gannets from anthropogenic disturbance are likely to be age and population specific. While these rates point towards continued growth of this population, the confidence intervals around our estimates are large, highlighting the need for improved resighting efforts in long-term studies of this nature.     

Survival estimates for Royal Terns in southern California

ABSTRACT.   Once the most abundant large tern in California, populations of Royal Terns ( Thalasseus maximus ) are now greatly reduced statewide. However, these terns are still common in southern California where the population appears to be increasing. We estimated survival of this species, for which no robust estimate of survival is available, using mark-resighting data. Apparent survival of birds >3 yr of age was estimated to be ∼0.95; first-year survival was lower at 0.86. The lower survival estimate for first-year birds probably reflects increased mortality, but could also be a function of permanent emigration by individuals in this age class. The adult survival probability is the highest reported among terns and suggests that survival is playing an important role in the recovery of this tern population and that the current population growth is not solely due to immigration. Improvements in resighting protocols, marking technology, and mark-recapture methods are recommended to better use live resighting, dead recovery, and multistate data.     

Experimental duck plague in blue-winged teal and Canada geese

Ten adult blue-winged teal (Anas discors) and six Canada goose (Branta canadensis) goslings were inoculated with liver tissue from a natural case of duck plague in a wild mallard (Anas platyrhynchos). Four additional teal were placed in contact with the inoculated ducks. Inoculated teal died 63.5-68 hr after inoculation; two of the contact teal died 161-162 hr after exposure. Three of the goslings died 119-133 hr after inoculation, the others were killed when moribund 90-133 hr postinfection. The clinical course of disease was extremely rapid in both species. Signs were limited to sudden onset of profound weakness, ataxia, tremors and terminal convulsions. The only consistent gross lesion in the teal was a small dark spleen; half the teal also had inconspicuous foci of epithelial necrosis in the distal esophagus and in the cloaca. Goslings had more severe lesions, with focal hepatic necrosis visible in all, and mucosal necrosis over the intestinal lymphoid tissue, and intestinal hemorrhage in three birds each. Microscopic lesions in both species were similar to those reported in mallards. Duck plague might be overlooked at necropsy of blue-winged teal, because of the paucity of gross lesions.     

Experimental quantification of long distance dispersal potential of aquatic snails in the gut of migratory birds

Many plant seeds and invertebrates can survive passage through the digestive system of birds, which may lead to long distance dispersal (endozoochory) in case of prolonged retention by moving vectors. Endozoochorous dispersal by waterbirds has nowadays been documented for many aquatic plant seeds, algae and dormant life stages of aquatic invertebrates. Anecdotal information indicates that endozoochory is also possible for fully functional, active aquatic organisms, a phenomenon that we here address experimentally using aquatic snails. We fed four species of aquatic snails to mallards (Anas platyrhynchos), and monitored snail retrieval and survival over time. One of the snail species tested was found to survive passage through the digestive tract of mallards as fully functional adults. Hydrobia (Peringia) ulvae survived up to five hours in the digestive tract. This suggests a maximum potential transport distance of up to 300 km may be possible if these snails are taken by flying birds, although the actual dispersal distance greatly depends on additional factors such as the behavior of the vectors. We put forward that more organisms that acquired traits for survival in stochastic environments such as wetlands, but not specifically adapted for endozoochory, may be sufficiently equipped to successfully pass a bird's digestive system. This may be explained by a digestive trade-off in birds, which maximize their net energy intake rate rather than digestive efficiency, since higher efficiency comes with the cost of prolonged retention times and hence reduces food intake. The resulting lower digestive efficiency allows species like aquatic snails, and potentially other fully functional organisms without obvious dispersal adaptations, to be transported internally. Adopting this view, endozoochorous dispersal may be more common than up to now thought.     

5. A NOTE ON THE PARADISE WHYDAHS

Vernon, C. J. 1975. Seventeenth ringing report for southern African. Ostrich 46:125-128.

A report on ringing activities in southern Africa from July 1973 to June 1974 is presented. A total of 51 561 birds of 451 species were ringed and are analysed according to distribution of ringers, groups of species and recovery rates. A list of those birds living longer than ten years is given. Analyses are needed of the most frequently ringed species in order to give greater purpose to future ringing.     

Influence of body condition on influenza A virus infection in mallard ducks: experimental infection data

Migrating waterfowl are implicated in the global spread of influenza A viruses (IAVs), and mallards (Anas platyrhynchos) are considered a particularly important IAV reservoir. Prevalence of IAV infection in waterfowl peaks during autumn pre-migration staging and then declines as birds reach wintering areas. Migration is energetically costly and birds often experience declines in body condition that may suppress immune function. We assessed how body condition affects susceptibility to infection, viral shedding and antibody production in wild-caught and captive-bred juvenile mallards challenged with low pathogenic avian influenza virus (LPAIV) H5N9. Wild mallards (n = 30) were separated into three experimental groups; each manipulated through food availability to a different condition level (−20%, −10%, and normal ±5% original body condition), and captive-bred mallards (n = 10) were maintained at normal condition. We found that wild mallards in normal condition were more susceptible to LPAIV infection, shed higher peak viral loads and shed viral RNA more frequently compared to birds in poor condition. Antibody production did not differ according to condition. We found that wild mallards did not differ from captive-bred mallards in viral intensity and duration of infection, but they did exhibit lower antibody titers and greater variation in viral load. Our findings suggest that reduced body condition negatively influences waterfowl host competence to LPAIV infection. This observation is contradictory to the recently proposed condition-dependent hypothesis, according to which birds in reduced condition would be more susceptible to IAV infection. The mechanisms responsible for reducing host competency among birds in poor condition remain unknown. Our research indicates body condition may influence the maintenance and spread of LPAIV by migrating waterfowl.