Tomasz Janiszewski

Center-Periphery Gradients of Chick Survival in the Colonies of Whiskered Terns Chlidonias hybrida may be Explained by the Variation in the Maternal Effects of Egg Size

Abstract. Central parts of avian colonies provide better safety against predators and, thus, are likely to be occupied by pairs of high quality. Therefore, spatial variation in the quality of breeders and predation rate within colonies should be directly reflected by the gradients of breeding success and chick survival. We have investigated relationships between nest location characteristics and survival of Whiskered Tern Chlidonias hybrida chicks in the colony at Jeziorsko reservoir, central Poland. We found that pairs nesting in the central, densely occupied areas of subcolonies had higher chick survival rates in comparison to edge pairs. There was also strong support for the positive effect of egg size and the negative effect of hatching date on the chick survival. Since pairs breeding in the central parts of subcolonies laid eggs of greater size and initiated laying earlier, we suggest that within-colony patterns of chick survival could be primarily attributed to the spatial variation in parental quality rather than to the higher predation pressure in the peripheral zones of the colony. There was also a moderate support for age variation in the survival rates of chicks, which ranged from 0.72 ± 0.06 to 0.91 ± 0.07 in different 5-day intervals of pre-fledging period. The survival of chicks over the entire pre-fledging period was estimated at 0.29–0.33, depending on the model.

Reproductive consequences of early arrival at breeding grounds in the White Stork Ciconia ciconia

Capsule The phenology of arrival at the breeding grounds and reproductive output of White Storks were studied in central Poland between 2000 and 2011. Although, in general, there was a strong negative relationship between the number of fledglings raised and arrival date, pairs in which both partners arrived at breeding grounds very early in spring (before 5 April) reared lower number of fledglings in comparison to pairs that arrived slightly later (between 5 and 14 April). In the studied population, the negative reproductive effects of exceptionally early arrival were associated with higher probability of entire brood loss. The probability of brood loss in pairs that arrived before 5 April was estimated at 0.22, which decreased to 0.10 in pairs that arrived between 5 and 14 April.

Timing of arrival at breeding grounds determines spatial patterns of productivity within the population of white stork (Ciconia ciconia)

Early arrival at breeding grounds have important fitness consequences for migratory birds, both at individual and population level. The aim of this study was to investigate how the timing of arrival at the breeding territories affects the spatial patterns of reproductive success within a population of white storks (Ciconia ciconia). Data were gathered annually for ca. 200 pairs of storks breeding in central Poland between 1994 and 2011. Geostatistical analysis of data indicated that in years of delayed arrival of the population (measured by the first quartile arrival date), the reproductive output of storks was negatively autocorrelated, which indicated that there was a tendency for pairs of high breeding success to neighbour with pairs of low success. By contrast, in years when first storks returned in early dates to the breeding grounds, their reproductive success did not show any kind of spatial autocorrelation. These results suggest that delayed return of the first-arriving storks of the population may increase intensity of intra-specific competition to the level at which high-quality breeding pairs monopolize most of available resources at the expense of neighbouring low-quality pairs, which have lower reproductive success as a consequence. Such hypothesis was further supported with the analysis of nesting densities, showing that the late-arriving breeding pairs incurred greater fitness costs (or derived lower fitness benefits) while breeding in high densities comparatively to the early-arriving conspecifics.

Adjustments and Exploitation of Body Stores During Post-Juvenile Molt in Common Snipe Gallinago gallinago

Abstract. Post-juvenile molt of Common Snipe was investigated during 2004-05 at the Jeziorsko reservoir, central Poland. Body mass and mass of fat stores were dependent on the stage of post-juvenile molt. The body mass increased prior to the commencement of molt, but during the intensive stage of the process it decreased and returned to the previous level. Fat-free body mass increased during molt, which may be attributed to increased protein synthesis or the higher water content of growing feathers. Fat stores were similar in snipe before and in the initial stage of molt; however, they decreased significantly during the transition to the intensive stage of the process. In total, snipe lost approximately 57% of the mass of fat loads over the course of molt (4.9% of lean body mass). Being a highly energetic constraint, post-juvenile molt is suggested to affect certain life history traits of Common Snipe such as the length of the staging periods during the autumn migratory period.

The Migration System of Common Snipe Gallinago gallinago on Autumn Passage Through Central Europe

The Common Snipe Gallinago gallinago migrates in large numbers through central Europe towards its wintering grounds in western Europe. Over the past 20 years more than 12 000 Common Snipes were ringed at seven ringing stations in Poland during their autumn migration. Birds migrating along the Baltic coast tended to spend the winter in more northern areas than those that used southern Poland as stopover sites during migration. This pattern supports the hypothesis of a parallel autumn migration exhibited by Common Snipe. Additionally, snipes passing through Poland at the beginning of the autumn migration (originating from near breeding areas) overwintered further north than later migrants (known to originate from more northern areas), which is consistent with a leap-frog migration pattern. Our results suggest that the migration pattern of the Common Snipe is more complex than previously thought, because these birds use a combination of two different non-exclusive migratory patterns.

A new insight into the ageing of Common Snipe Gallinago gallinago ‐ the value of contrast within the wing coverts of adults

The ageing criteria for Common Snipe Gallinago gallinago are complex, and a significant proportion of birds in autumn which have completed moult cannot be aged. Jeziorsko Reservoir is an important stopover site for Common Snipe during autumn migration through central Poland. Detailed studies of wing coverts show that in a proportion of adult birds a contrast or moult limit between old, faded feathers and new ones grown during the moult can be used as an additional criterion to distinguish adults from first‐year birds that have completed their post‐juvenile moult. In particular, the presence of one or more old humeral coverts allowed a high proportion of birds, otherwise of indeterminate age, to be identified as adults. Since these feathers are normally hidden under the scapulars, careful plumage examination is needed to age birds correctly.

Ecological, physiological, and morphological correlates of blood hemoglobin concentration in a migratory shorebird.

The information on the phenotypic and ecological factors that influence hemoglobin concentration in free-living birds is scarce. In order to recognize sources of variation in hemoglobin levels of migratory shorebirds, we measured whole-blood hemoglobin concentration in 553 juvenile and 166 adult common snipe Gallinago gallinago during autumn migration through central Poland. Among the intrinsic determinants of hemoglobin concentration in common snipe, we identified traits such as age, wing morphology, developmental stability, nutritional condition, and molt. We found that adult birds had higher hemoglobin concentrations than juveniles. Hemoglobin concentration was not related to body size, but it correlated with wing morphology. In adult males there was also a positive relationship between hemoglobin concentration and developmental stability, measured by fluctuating asymmetry in wing shape. The process of molt was found to affect blood hemoglobin concentration in both juvenile and adult common snipe, as the lowest concentrations were recorded in the initial stages of molt. Finally, we recorded a gradual increase in hemoglobin concentration of juvenile and adult snipe over the course of the autumn migratory season, and this trend was attributed to higher fat loads carried by late migrants. Hemoglobin concentration also correlated with other indices of nutritional state, such as plasma concentrations of proteins. All this clearly indicates that hemoglobin concentration may reflect a wide range of physiological processes, but in spite of this immense variation, it is likely to reliably indicate phenotypic quality of birds.

Hemoglobin concentrations in waders vary with their strategies of migration: A comparative analysis

The aim of this study was to determine whether blood oxygen capacity of waders varies with respect to migration at both inter-specific and individual level. To verify this hypothesis we measured hemoglobin concentration in 875 waders from 14 species during their autumn migration through central Poland. In most of the species we found an increase in the hemoglobin levels along with increasing fat loads during the stopover period, which suggests that individual birds are able to elevate their oxygen-carrying capacity of blood prior to departure on a migratory flight. Positive relationship between hemoglobin concentrations of waders and their fat loads was confirmed at the inter-specific level by the comparative analysis of independent contrasts. Comparative analysis also demonstrated that hemoglobin concentrations were positively related with theoretical flight range and mean refueling rate during stopovers. The results indicate that species traveling according to the strategy of energy-minimization (short-distance migrants, low fat reserves, low refueling rates) have lower blood oxygen capacity in comparison to time-selected species (long-distance migrants, high fat reserves, high refueling rates). It remains uncertain whether high hemoglobin levels in long-distance migrants are a fixed evolutionary trait or a temporal physiological adaptation associated with carrying considerable fat load.

Nest location affects chick growth rates in Whiskered Terns Chlidonias hybrida

Capsule Body mass of Whiskered Tern chicks from the central parts of subcolonies grew at a higher rate in comparison to chicks hatched in the peripheral zones. Growth rates of both body mass and head length correlated positively with nest density. We suggest that spatial distribution of pair quality within the colony of Whiskered Terns follows a central–periphery gradient.

Selective Forces Responsible for Transition to Nesting on Electricity Poles in the White Stork Ciconia ciconia

The process of transition from nesting on trees to electricity poles has been observed over the last decades in many European populations of the White Stork Ciconia ciconia, but the direct mechanisms behind this process have not been explicitly identified. The aim of this study was to identify selective forces responsible for transition to nesting on electricity poles using long-term data (1994–2011) collected for the central Polish population of c. 190 breeding pairs. We hypothesized that transition to nesting on electricity poles could be explained by two non-exclusive mechanisms. Firstly, the process could be driven by insufficient availability of traditional nesting sites in the vicinity of favourable foraging grounds. Secondly, nesting on electricity poles could be directly associated with fitness benefits resulting from different nest structure and microclimate. We found that the process of transition had started and proceeded at the highest rate in the good- and medium-quality areas of river valleys, where most intense competition for nesting territories and highest stork densities were recorded. By contrast, we found little support for direct fitness benefits associated with nesting on electricity poles. In fact, reproductive success (number of fledglings per pair) of storks nesting on poles was lower in comparison to those nesting on trees, but this relationship prevailed only in the areas of poor quality (dry agricultural landscape). The results strongly suggest that the process of transition to nesting on electricity poles in the White Stork is not facilitated by direct reproductive benefits, but could be driven by decreasing availability of natural nesting sites in the attractive breeding areas.