Individual Papers

8:55-9:20 AM How do geometric constraints influence migration patterns? - K. Thorup & C. Rahbek Null models exclusively invoking geometric constraints have recently been demonstrated to provide new insight as to what explains geographic patterns of species richness and range size distribution. Analyses of migration patterns have traditionally been conducted in the absence of appropriate simulations and analytical models. Here we present a null model exclusively invoking geometric constraints and a more advanced analytical model incorporating spread along a migration direction that allow investigation of the influence of physiographical and physiological boundaries for terrestrial taxa, with ocean and sea as geometric constraints, in relation to observed patterns of migration. Our models take into account the low recovery probability of terrestrial taxa over sea. The null model was not found to explain any of the directional variation in the ring-recoveries, but when comparing the distribution of data modeled using a simple clock-and-compass model with distributions of ring-recoveries, geometric constraints were found to explain up to 22% of the variation in ring-recoveries. However, the assumed directional concentrations per step used in the model were much higher than expected, and the qualitative fit of the model was rather poor even when non-terrestrial sites of recoveries were excluded. 9:20-9:45 AM Estimating dispersal in birds: taming the unknown. A.J. van Noordwijk A fundamental problem in measuring dispersal is that the observations made are restricted by the observations that could possibly be made. This quickly leads to a situation where the distribution of observers in time and space determines the observations more than the behaviour of the species studied. Although we will never know where individuals lost out of sight went to, or where immigrants came from, it is possible to obtain estimates of dispersal distances that have been corrected for distance specific observation probabilities (Thomson, van Noordwijk & Hagemeijer, J. Appl Stat in press). Here I want to explore a complementary approach, we can use the frequency of immigrants of unknown origin as an estimate of the unknown part of a 'dispersal as a function of distance' curve. Getting a number for how much we don't know allows us to get a better perspective on what we do know. In nearly all data sets, we will have a short range of distances in which nearly all potential recruits were marked, a further range of distances in which a proportion of all potential recruits were marked and a furthest range of distances in which no potential recruits were marked. Where we can get an estimate of the proportion marked in the middle range, from population densities or distribution of suitable habitat, we can derive estimates for the numbers of immigrants coming from these distances. Although we cannot know where the rest of the immigrants came from, we do have an estimate of "the total area under the curve" of the furthest distances. I will apply these ideas to data on natal dispersal in Swallows, Blue Tits and Great Tits. This approach will allow us to compare dispersal curves between groups (e.g. sexes), but also curves for the same species among areas differing in the distribution of suitable habitat (differing in fragmentation). 9:45-10:10 AM Multistate modeling of movement and philopatry of breeding ross's geese - K. Drake & R. Alisauskas We estimated rates of breeding philopatry and dispersal within the Queen Maud Gulf metapopulation of Ross's Geese (Chen rossii) using multistate modeling of neckband observations at five breeding colonies, 1999-2002. Philopatry was female-biased, but probability of philopatry varied among colonies. Despite probabilities of =0.62 for breeding philopatry to a given colony by either sex, this study demonstrates that annual movement among breeding colonies was substantial, and greater than previously assumed. We provide behavioral evidence (consistent with genetic studies which suggested little or no phylogeographic structure in the closely-related lesser snow goose, Chen caerulescens) for extensive interconnectedness among breeding populations. High likelihood of annual movements among colonies emphasize (1) the influence of dispersal on changes in breeding distribution, and (2) provides insight about the contributions of emigration and immigration to colony-specific population growth rates. Although movement was the primary parameter of interest, estimates of male survival from multistate modeling differed from survival estimates from band recovery models, whereas female survival estimates were consistent with those from band recovery models. We suspect the difference between sexes in survival estimated from multistate models was due to higher rates of neckband loss in males compared to females, as has been found in numerous other studies, and/or higher rates of permanent emigration by males from sampled areas. The importance of violating model assumptions depends upon the biological parameter of interest, and whether inference is restricted to the sample population or extended to the entire metapopulation. 10:25-10:45 AM Modelling Dolphin Behaviour using Multi-State Models with Time-Varying Covariates - S. Brooks & R. King Effective management is the key to the protection of many endangered species. Identification of the primary factors affecting survival will often lead to the introduction of strategies to improve survival rates. In this talk, we consider a small population of Hector's dolphins located of the coast of New Zealand and the impact that the establishment of a seasonal sanctuary has on their survival and migration rates. We use a multi-state model to describe the movement of the dolphins around the habitat and adopt a Bayesian approach using reversible jump Markov chain Monte to distinguish between a wide range of competing models. We also examine the impact of the inclusion of time-varying covariates such as catch-effort information and demonstrate the added value that these data provide in terms of both model discrimination and parameter estimation. In particular, we find a whole class of models that provide a far better fit to the data (and therefore better prediction and ultimately better management) than those adopted in previous analyses. 10:45-11:05 AM Spatial distribution of breeding Pied Flycatchers Ficedula hypoleuca in respect to their natal sites - L. Sokolov, N. Chernetsov, V. Kosarev, D. Leoke, M. Markovets, A. Tsvey, A. Shapoval Research project on the study of philopatry and dispersal of Pied Flycatchers Ficedula hypoleuca has been underway on the Courish Spit on the Baltic since 1980. A total of 8006 nestlings were ringed in the Russian part of the Courish Spit. In subsequent years, 512 individuals (6,4%) were recaptured in the whole study plot, 300 males and 212 females. The aim of this study was to test two alternative hypotheses proposed to explain the distribution of breeding Pied Flycatchers in respect to their natal site. The breeding area imprinting hypothesis (Löhrl 1959, Berndt & Winkel 1979, Sokolov et al. 1984) assumes that in spring, migrants try to return to a relatively small area, with a radius of one to several km. The other hypothesis forwarded by Vysotsky (2001) suggests that all first-year birds and many adults in spring arrive randomly to an area much larger than the initial study area. In 2000, some 800 nest-boxes were added so that their overall number reached 1340 and the length of the study plot reached 44 km. To study natal dispersal, we compared the observed distribution of natal dispersal distances with the distribution derived from the model assuming random arrival to the study area. Significantly more Pied Flycatchers were recaptured within several km from the natal site that at larger distance, and this was not a function of the control effort. Therefore, it is concluded that the home area imprinted by juvenile Pied Flycatchers has a diameter of several kilometres and not several dozens of kilometres. 11:05-11:25 AM Timing and routes of migration based on ring recoveries and randomization methods - H. Lokki & P. Saurola In the first EURING Technical Meeting we recommended randomization tests for comparing wintering areas of different species or cohorts of birds on the basis of ring recoveries. In this contribution we will use randomization methods when trying to answer the following important questions of migration studies: Do the timing and/or routes of migration of different species, sexes or age classes differ from each other? Can anything statistically sound be inferred from ring recoveries? As a rule, the data consists of non-normally distributed recovery records (ti, x(ti), y(ti)) where x(ti) are longitudes, y(ti) latitudes of birds recorded in N dates ti, i = 1, 2, … , N. We assume that these records constitute a representative sample of places where the birds have been found during their lives. At first, in order to sum up the information included in the recovery locations in an "average route", we create a time-window and slide it through the set of recoveries. In each time-window we sample the records with replacement and compute the average of the records in the sample. By repeating this procedure many times we obtain an empirical distribution of the average. Then we combine these distributions computed for each time-window to get the average route of the birds. For comparing two routes, we compute the difference of the averages of the records of the two groups in each time-window. Then we compute the sum of the differences. In order to find out whether or not the observed sum of differences is statistically significant we compute the empirical distribution of the sum of differences as follows. In each time-window we randomize many times the inclusion of records into the two groups. Then we compute differences of the averages of the randomized groups and accordingly the sums of the differences. The ranking of the observed sum in the empirical distribution of the sums of differences determines whether or not the two routes are similar geographically and in respect of timing. Finally we illustrate the methods with data sets extracted from the Finnish recovery database. 11:25-11:45 AM Multistate modeling of brood amalgamation in white-winged scoters (melanitta fusca deglandi) - Joshua J. Traylor, Ray T. Alisauskas, and F. Patrick Kehoe There is a proclivity for female North American waterfowl to lose or abandon offspring after hatch. Often these abandoned ducklings are subsequently brooded by foster hens giving rise to the phenomena of post-hatch brood amalgamation (PHBA). The potential fitness implications that arise from this behavior has brought about considerable debate on physiological or ecological motivations for PHBA of young, and potential costs and benefits of ducklings brooded in amalgamated broods. Few studies have estimated the effects of PHBA on offspring survival and have not followed individually marked offspring: most studies have been restricted to studying PHBA based on maternal characteristics because only broods have been individually color marked. Here, we explore relationships between probabilities of movements from maternal to amalgamated broods by using a population of individually marked white-winged scoters (i.e., females and offspring) (Melanitta fusca deglandi) and pertinent ecological covariates utilizing multistate modeling. We tested hypotheses about movement probabilities and 1) hatch date, 2) brood size, 3) female size and condition, 4) duckling size and condition, and 5) weather. We defined ducklings as belonging to one of 3 social strata: (A) natal mother with no foster ducklings, (B) foster mother and conspecific non-siblings, (C) natal mother with conspecific non-siblings and limited our study of movement probabilities to two weeks after hatch because this period is when most mortality and movement occurred. Thus, we estimated probabilities of survival, recapture, and movement for each stratum focusing on covariates for movement. We evaluate hypotheses suggested to motivate PHBA (e.g., accidental mixing, brood size and brood success, and energetic stress hypotheses) and evaluate the influence on duckling survival. Because the importance of predation in motivating abandonment or adoption of ducklings remains equivocal, we discuss how duckling traits, in a population located near high gull densities, may provide insights into the relative importance of predation to PHBA.