Veli-Matti Pakanen

Nest predation and trampling as management risks in grazed coastal meadows

Livestock grazing is an important management tool of agri-environment schemes initiated within the European Union to maintain and restore biodiversity of grassland birds. However, grazing can affect bird populations negatively by depressing reproduction through nest trampling and increasing nest predation. These effects are, however, considered low when using recommended stocking rates. By simulating wader nests, we experimentally quantify and examine the causes of variation in trampling rates on managed Baltic coastal meadows. Secondly, we examine whether livestock presence increases nest predation of one management target, the critically endangered southern dunlin (Calidris alpina schinzii). Trampling rates of experimental nests were high. Only 21% of nests would have survived a three week incubating period early in the grazing season. Trampling rates were most severe at the onset of grazing and decreased with time. Thus, timing of grazing plays a crucial role in determining breeding success on managed meadows. Predation rates of dunlin nests were moderate and did not depend on livestock presence suggesting that incubating dunlin are not disturbed by cattle. While grazing is vital in habitat restoration and in conserving grassland biodiversity, our results suggest that grazing may also threaten the viability of populations if negative effects are underestimated. Therefore, management plans, especially for endangered species, should not only rely on general recommendations on stocking rates but instead planners need to evaluate the significance of negative effects in terms of local conditions (timing of breeding and grazing, space use of cattle and birds, measured trampling rates) and adjust grazing practises accordingly.

Population genetic structure in the Temminck's stint Calidris temminckii, with an emphasis on Fennoscandian populations

Temminck’s stint breeds in Eurasian arctic tundra and subarctic and temperate boreal zones in a range extending from Fennoscandia to easternmost Siberia. In contrast to the favourable global conservation status of the species, it has been classified as vulnerable in Finland and near threatened in Sweden. A fragment of the control region of mtDNA was sequenced from 127 individuals from breeding areas in Fennoscandia in the west (three populations) and in the eastern end of the range. The mtDNA variability and structuring were among the lowest values reported for waders (FST −0.02616). The mtDNA sequences revealed seven haplotypes, of which four were present in single individuals. The most common haplotype occurred in 81% of all individuals and in all birds in the Siberian sample. There was evidence of two maternal lineages. The most common lineage occurred in 95% of the individuals and was the only one present in the Siberian sample. The lineages coexisted in all three Fennoscandian populations, indicating a secondary contact of two previously isolated populations. The mtDNA variation and the mitochondrial nucleotide and haplotype diversities indicated panmixis of the populations. However, a higher degree of population differentiation was detected in microsatellite allele frequencies (125 birds, six loci) in Fennoscandia between the Bothnian Bay population and the two inland populations (Lapland and southern Norway). The difference may be caused by the female-biased dispersal pattern of the species. In addition, the Bothnian Bay population appeared to be genetically bottlenecked, an observation in concordance with the recent decimation of the population.

Larval melanism in a geometrid moth: promoted neither by a thermal nor seasonal adaptation but desiccating environments

Spatiotemporal variation in the degree of melanism is often considered in the context of thermal adaptation, melanism being advantageous under suboptimal thermal conditions. Yet, other mutually nonexclusive explanations exist. Analysis of geographical patterns combined with laboratory experiments on the mechanisms of morph induction helps to unveil the adaptive value of particular cases of polyphenism. In the context of the thermal melanism hypothesis and seasonal adaptations, we explored an array of environmental factors that may affect the expression and performance of nonmelanic vs. melanic larval morphs in different latitudinal populations of the facultatively bivoltine moth Chiasmia clathrata (Lepidoptera: Geometridae). Geographical variation in larval coloration was independent of average temperatures experienced by the populations in the wild. The melanic morph was, however, more abundant in dry than in mesic habitats. In the laboratory, the melanic morph was induced especially under a high level of incident radiation but also at relatively high temperatures, but independently of photoperiod. Melanic larvae had higher growth rates and shorter development times than the nonmelanic ones when both temperature and the level of incident radiation were high. Our results that melanism is induced and advantageous in warm desiccating conditions contradict the thermal melanism hypothesis for this species. Neither has melanism evolved to compensate time constraints due to forthcoming autumn. Instead, larvae solve seasonal variation in the time available for growth by an elevated growth rate and a shortened larval period in the face of autumnal photoperiods. The phenotypic response to the level of incident radiation and a lack of adaptive adjustment of larval growth trajectories in univoltine populations underpin the role of deterministic environmental variation in the evolution of irreversible adaptive plasticity and seasonal polyphenism.

Migration and Wintering of Baltic Dunlins Calidris Alpina Schinzii with Known Breeding Origin

The population of Baltic Dunlins Calidris alpina schinzii is very small and is declining rapidly. To optimize conservation efforts, knowledge about the location of staging and wintering sites is crucial. As part of intensive studies on Dunlins in Finland, Sweden, Denmark and Germany during the last 40 years, chicks and breeding adults have been marked, which has resulted in 110 recoveries during migration and winter. The majority of these recoveries are from western and northern Europe during the months immediately before and after the breeding season (21 February to 16 August), whereas there are only ten recoveries outside this period. Five of these ten recoveries, including four of six midwinter recoveries, are from N and NW Africa (Mauritania, Tunisia and Morocco). Given the relatively small probability of obtaining recoveries from these areas, the data indicate that the main wintering areas of the Baltic Dunlin are the estuaries in northern Africa, which it shares with other European and Nearctic populations of small-sized Dunlins breeding in Greenland, Svalbard, Iceland, Faeroe Islands, Ireland and Great Britain, The autumn migration period of the Baltic Dunlin is so short that the post-breeding moult must take place primarily at the wintering grounds. During spring and autumn, the Baltic Dunlin migrates well before the larger and much more numerous alpina subspecies, which breeds in arctic Eurasia. The recovery data suggest that the estuaries in the Baltic, the Wadden Sea, SE and S England, the Atlantic seaboard in France, and the Iberian Peninsula are of similar importance for the Baltic Dunlin as they are for the alpina Dunlins.

Grazed wet meadows are sink habitats for the southern dunlin (Calidris alpina schinzii) due to nest trampling by cattle

Abstract The effect of habitat management is commonly evaluated by measuring population growth, which does not distinguish changes in reproductive success from changes in survival or the effects of immigration or emigration. Management has rarely been evaluated considering complete life cycle of the target organisms, including also possible negative impacts from management. We evaluated the effectiveness of cattle grazing in the restoration of coastal meadows as a breeding habitat for small and medium‐sized ground‐nesting birds by examining the size and demography of a southern dunlin (Calidris alpina schinzii) breeding population. Using a stochastic renesting model that includes within‐season variation in breeding parameters, we evaluated the effect of grazing time and stocking rates on reproduction. The census data indicated that the population was stable when nest trampling was prevented, but detailed demographic models showed that the population on managed meadows was a sink that persisted by attracting immigrants. Even small reductions in reproductive success caused by trampling were detrimental to long‐term viability. We suggest that the best management strategy is to postpone grazing to after the 19th of June, which is about three weeks later than what is optimal from the farmers point of view. The differing results from the two evaluation approaches warn against planning and evaluating management only based on census population size and highlight the need to consider target‐specific life history characteristics and demography. Even though grazing management is crucial for creating and maintaining suitable habitats, we found that it was insufficient in maintaining a viable population without additional measures that increase nest success. In the presently studied case and in populations with similar breeding cycles, impacts from nest trampling can be avoided by starting grazing when about 70% of the breeding season has past.

Sex-specific mortality costs of dispersal during the post-settlement stage promote male philopatry in a resident passerine

The costs and benefits of dispersal that select for sex-biased dispersal are still poorly understood. Many studies examine fitness consequences of dispersal after first breeding, while dispersal costs are most likely paid before first breeding during the movement, settlement, and post-settlement stages. We studied survival correlates of dispersal between flock settlement and first breeding during the first winter of juvenile willow tits (Poecile montanus), a small passerine that has female-biased natal dispersal, but shows no dispersal-associated survival differences after first breeding. This resident food-hoarding species winters in small stable non-kin territorial flocks. We collected capture-recapture data by following flocks from autumn to the following spring. We compared monthly survival and return rates of juveniles that were born and recruited within the study area (philopatric juveniles) and juveniles that originated from outside the study area (immigrant juveniles). Among males, survival was highest for philopatric juveniles whereas survival of females was higher among immigrant juveniles, providing one explanation for the female-biased natal dispersal observed in the species. Philopatric males may benefit from prior residency either through increased site familiarity and knowledge of winter food resources and/or by gaining higher social ranks during flock establishment. However, rank data provided little support for the latter hypothesis. Other mechanisms such as increased ability to find high-quality flocks and mates may be important for female survival. Our results provide further evidence that dispersal costs are paid mainly before first breeding and that sex-specific costs of dispersal play a role in the evolution of sex-biased dispersal.Significance statementThis paper shows that female-biased dispersal can be a consequence of sex-specific costs and benefits of dispersal during the post-settlement stage of the dispersal process which is a very poorly understood stage in dispersal theory. By examining correlates of dispersal before rather than after first breeding as it is usually done, our study aids in understanding the selection pressures modifying dispersal strategies. Our results have wide applicability because there are many resident taxa similar to the willow tit (our study species) that have a settlement stage and a prolonged non-reproductive phase before their first reproduction.

Apparent adult survival of the critically endangered Baltic Dunlin Calidris alpina schinzii during a period of strong population decline

ABSTRACT Capsule: Apparent adult survival of the critically endangered Baltic Dunlin Calidris alpina schinzii, showed evidence of a decline between 1990 and 2006 from 0.817 to 0.650. Aims: In Europe, declines in wet-grassland breeding waders have been attributed to changes in breeding habitat but long-term information on survival is rare. We examined whether adult survival of the Baltic Dunlin declined during a period of strong population decline. Methods: We modelled apparent survival using Cormack–Jolly–Seber models and long-term capture–recapture data collected from a Danish population. We fitted models that constrained apparent adult survival with linear and quadratic trends, and compared them with constant and time dependent models to test whether survival declined during the study period. Results: Models including linear and quadratic trends were most supported. However, the trend variables explained only 24–35% of observed temporal variance suggesting that a large portion of variation in survival remained undescribed. Model averaged estimates indicated a decline in adult survival from 0.817 to 0.650 between 1990 and 2006 with increased uncertainty towards the end. Conclusion: Our results suggest that gradual long-term changes in adult survival may have contributed to the decline of the Baltic Dunlin.

Cold weather increases winter site fidelity in a group-living passerine

AbstractSite fidelity during the non-breeding season is beneficial if habitat quality and environmental predictability are high. In group-living species, the costs and benefits of site fidelity may be linked to the non-social (weather) and social (dominance hierarchy) environments, but little is known about factors influencing movements during the non-breeding season. We studied both within- and between-winter site fidelity of the great tit (Parus major), a partial migrant in northern Finland. We collected mark-resight data on wintering great tits across two winters at multiple sites, and tested for the effects of age, sex, season, temperature and day length on site fidelity. Within-winter movement was lower during mid-winter and decreased during cold periods. This pattern is probably linked to energy saving and predator escaping strategies during these demanding periods when energy expenditure is high and birds have limited daylight hours to forage. Site fidelity was lower for juveniles than adults within a winter, but it was unaffected by sex. These results agree with an age related dominance structure and site-specific dominance found in great tits, but they can also be related to prior experience as young individuals still collect information during their first winter. In contrast, between-winter site fidelity was not affected by age or sex, suggesting equal benefits from site fidelity. Juveniles probably gather information on resource abundance and distribution in their first winter, and thereby gain the same benefits as adults from returning the next winter.ZusammenfassungKaltes wetter im winter erhöht die standorttreue sozial lebender sperlingsvögel Standorttreue außerhalb der Brutperiode ist dann von Nutzen, wenn die Habitatqualität hoch und die Umgebungsbedingungen stabil sind. Bei in Gruppen lebenden Arten hängen Kosten und Nutzen von Standorttreue möglicherweise auch mit nicht-sozialen Faktoren (Wetter) und mit sozialen Umgebungsbedingungen (Dominanz-Hierarchien) zusammen. Man weiß aber nur wenig über Faktoren, die die Ortsveränderungen der Vögel außerhalb der Brutsaison beeinflussen. Wir untersuchten die Standorttreue der Kohlmeise (Parus major), einem Teilzieher in Nord-Finnland, sowohl während des Winters als auch zwischen Wintern. Hierfür sammelten wir an unterschiedlichen Standorten Wiederfang-Daten von Kohlmeisen und untersuchten diese auf mögliche Auswirkungen von Geschlecht, Alter, Saison, Temperatur und Tageslänge auf die Standorttreue. Die Ortsveränderungen waren während des Mittwinters geringer und nahmen während Kälteperioden ab. Dieses Verhaltensmuster steht wahrscheinlich in Zusammenhang mit Strategien zum Sparen von Energie und Vermeiden von Räubern während dieser schwierigen Jahreszeit, wenn der Energieverbrauch hoch ist und den Vögeln nur wenig Tageslicht zum Futtersammeln bleibt. Während des Winters zeigten Jungtiere weniger Standorttreue als ältere Tiere, ein Zusammenhang mit dem Geschlecht konnte jedoch nicht nachgewiesen werden. Diese Ergebnisse passen gut zu einer von Kohlmeisen bekannten altersabhängigen Dominanz-Struktur sowie Standort-spezifischen Dominanz. Sie können aber auch zu früheren Erfahrungen der Vögel in Beziehung gesetzt werden, da Jungtiere während ihres ersten Winters noch Informationen sammeln. Im Gegensatz dazu gab es in der Zeit zwischen Wintern keinerlei Einfluss vom Alter und Geschlecht der Vögel auf die Standorttreue. Jungtiere sammeln wahrscheinlich in ihrem ersten Winter Informationen zum Vorhandensein und der Verbreitung von Nahrungsquellen, was ihnen vermutlich die gleichen Vorteile schafft wie älteren Tieren, die im nächsten Winter wiederkehren.

Apparent survival, territory turnover and site fidelity rates in Northern Goshawk Accipiter gentilis populations close to the northern range limit

ABSTRACT Capsule: Mark–recapture data suggest low apparent survival and sex- and population-specific site fidelity and territory turnover in adult Northern Goshawks Accipiter gentilis breeding in northern Europe. Aims: To understand how species cope with global environmental change requires knowledge of variation in population demographic rates, especially from populations close to the species’ northern range limit and from keystone species such as raptors. We analyse apparent survival and breeding dispersal propensity of adult Northern Goshawks breeding in northern Europe. Methods: We used long-term mark–recapture data from two populations in Finland, northern Europe, and Cormack–Jolly–Seber models and binomial generalized linear models to investigate sex- and population-specific variation in apparent survival, territory turnover and site fidelity. Results: We report low apparent survival (53–72%) of breeding adult Goshawks. Breeding dispersal propensity was higher in females than males, especially in northern Finland, contrasting with previous studies that suggest high site fidelity in both sexes. Conclusion: Low apparent survival in females may be mainly due to permanent emigration outside the study areas, whereas in males the survival rate may truly be low. Both demographic aspects may be driven by the combination of sex-specific roles related to breeding and difficult environmental conditions prevailing in northern latitudes during the non-breeding season.