Volume 23 (2015): Issue 1 (June 2015)

Shortage of breeding sites is an important limiting factor of bird populations. Artificial breeding platforms, nest-boxes or man-made twig nests often present solutions with remarkable results, however long-term sustainability of these populations remains to be resolved. Furthermore, the question whether the inference of results of studies conducted on birds breeding in artificial breeding sites can be generalized to other populations, still remains open. Here we present the history, and the results of a 20 year old (1995-2015) nest-box programme initiated to increase potential breeding possibilities of Red-footed Falcons in an area, where nest-site shortage was a severe limiting factor. We show how various other species (Jackdaws, Kestrels and Long-eared Owls) have utilized these resources, and present descriptive statistics on their reproductive performance. Analysing the data of a total of 1432 breeding attempts, we show that Red-footed Falcons have similar clutch sizes, and nesting success (i.e. ratio of nests with at least on fledgling), however fledging success (ratio of the number of eggs/fledged nestlings) was different in artificial nest-boxes. When we excluded closed box types from artificial nests, this difference was not apparent. In case of Kestrels (n=1626 breeding attempts) clutch size was significantly higher in artificial nests, while we found no difference in fledging or nesting success. When only comparing open boxes to natural nests, the difference in clutch size was no longer significant. We also analysed the effect of nest box design on reproductive parameters of the two species using regression trees. Inter annual effects were the most important in shaping clutch size and fledging rate of both falcon species, however we also found nest-box design effects, but only in Red-footed Falcons. In years when mean clutch size was high, these birds had lower clutch size in an older, darker nest-box type compared to an alternative design, and to open boxes. However, fledging rate in the same years was lower for both open boxes and older nest-boxes. We conclude that artificial colonies are an important and successful tool in Red-footed Falcon conservation, and that the breeding parameters measured in artificial colonies depend on nest-box design. We present correlative evidence that closed boxes have a significant positive species specific effect on reproduction, probably due to their protection against weather. We also show that birds may have a preference for a certain nest-box design, and that the breeding success in the less favoured box type may be similar to that in open nests. We recommend that future studies incorporate nest-type and nest-box design effects in all comparisons made on reproductive performance in case of Red-footed Falcons and Kestrels.

Active conservation measures often entail supplementing scarce resources, such as food or nesting site to high conservation value species. We hypothesized that adequate nest material in reasonable distance is a scarce resource for Rooks breeding in open grassland habitats of Hungary. Here we show that Rooks willingly utilize large quantities of provided excess nesting material, and that this procedure may alter nest composition, and increase the number of successful pairs. Our results show that while nest height remains constant, twig diameter is significantly larger, the number of twigs used per nest is presumably smaller, and that the ratio of nests with fledglings is higher in a rookery where supplementary twigs were present. Providing twigs and branches in the vicinity of rookeries may serve as an active conservation measure to increase the number of nests in a rookery, and thus the potential number of nesting possibilities for Red-footed Falcons.

We studied hunting success of 13 male Red-footed Falcons by radio-telemetry in the second phase of chick rearing. We coded 484 hunting events, and the success measured in captured prey biomass/minute was exceedingly high in corn fields. This is mainly caused by the fact that the effectiveness of hunting for vertebrate prey was high on the harvested stubble fields. Moreover the observed falcons hunted for insects in these stubble field and alfalfa fields most successfully. In the studied habitat the chick feeding period of Red-footed Falcons coincide with the harvest of cereal fields, and the suddenly created lower vegetation cover increases temporarily the accessibility of prey items.

Till they were available and could be efficiently harvested, the falcons hunted on the fields within a 1 km radius from the nesting colony for the more profitable vertebrate prey. Thereafter they searched for vertebrate prey on the fields located at average 1–2.5 km distance from the colony. In the later zone falcons started to hunt insects, too, but approximately third of the captured insects (36.4%) was consumed immediately and was not delivered to the colony. Conversely larger prey was almost always (98.1%) carried directly to the nest site. Only one part of the Field Voles was observed to be eaten regularly: the brain. Finally later in the breeding season falcons were observed more and more often to hunt in the nearest fields again, this time for insects. Probably due to the depletion of the distant plots, the closer fields with lower investment became a competitive alternative for the birds.

Our results highlight the fact that even for such characteristic short-grass specialist birds as Red-footed Falcons the prey sources offered by arable lands might be temporarily exploited with success. Hence it is very important to integrate the measures offered by agri-environment schemes into the management of this threatened species.

Orthopterans play an important role in Red-footed Falcon diet, however, most studies focus only on its qualitative food composition, and less on quantitative composition and preferences of the taxa identified as prey. During the present research, an extensive orthopterological investigation was carried out in the Red-footed Falcon study area, Vásárhelyi Plain (SE-Hungary) between 2006 and 2008. Grasshoppers were sampled in their main habitats by sweep netting and pitfall trapping, and orthopterans were identified in the food remnants collected from the nests, both artificial and natural ones. 26 species were detected during the field works, 18 species from the food remnants. Altogether 32 species were identified. Prey preference values for all species for each year were calculated. More than two thirds of the identified preys were Decticus verrucivorus, and nearly 20% were Tettigonia viridissima. Other common prey species were Melanogryllus desertus, Platycleis affinis, Gryllotalpa gryllotalpa, Calliptamus italicus and Gryllus campestris. Based on the prey preference analysis, the most preferred species was Decticus verrucivorus with extreme high values, and the other preferred ones, overlapping with the previous list, were Platycleis affinis, Bicolorana bicolor, Tettigonia viridissima, Calliptamus italicus and Roeseliana roeselii. These results may help in the development of Red-footed Falcon-friendly habitats through the application of habitat management favourable for the preferred prey species.

Little is known about the louse species harboured by Red-footed and Amur Falcons despite the fact that various life-history traits of these hosts make them good model species to study host-parasite interactions. We collected lice samples from fully grown Amur (n=20) and Red-footed Falcons (n=59), and from nestlings of Red-footed Falcons (n=179) in four countries: Hungary, India, Italy and South Africa. We identified 3 louse species on both host species, namely Degeeriella rufa, Colpocephalum subzerafae and Laembothrion tinnunculi. The latter species has never been found on these hosts. Comparing population parameters of lice between hosts we found significantly higher prevalence levels of D. rufa and C. subzerafae on Amur Falcons. Adult Red-footed Falcons had higher D. rufa prevalence compared to C. subzerafae. For the first time we also show inter-annual shift in prevalence and intensity levels of these species on Red-footed Falcons; in 2012 on adult hosts C. subzerafae had higher intensity levels than D. rufa, however in 2014 D. rufa had significantly higher intensity compared to C. subzerafae. In case of nestlings both louse species had significantly higher preva lence levels than in 2014. The exact causes of such inter-annual shifts are yet to be understood.

Selecting a suitable breeding habitats and a nest-site within are crucial decisions birds have to make. Free ranging solitary Kestrels may use public information derived from leftover pellets and prey remnants from previous conspecific breeding attempts to assess location quality. However, this information may also indicate potentially higher nestling ectoparasite load. In colonies where habitat quality is similar for all available nests, the only information of previous nest usage may reflect expected future parasite pressure. In this study we explored whether Kestrels, Red-footed Falcons and Jackdaws rely on nest-material consisting of pellets and prey remnants when choosing a nest in a multi species artificial colony system. We also assessed potential effects of these decisions on reproductive success. We randomly selected and cleaned half (n=102) of all available nest-boxes in each of the studied 4 colonies before the breeding season. We then monitored occupancy, egg-laying date, hatching and fledging success. In case of Red-footed Falcons, we also acquired adult age and nestling condition data. Our results show that Kestrels were more likely to breed in uncleaned nest-boxes, however, eggs laid in cleaned nest-boxes were more likely to develop into fledged nestlings. There was a weak indication that lower hatching rate was responsible for this effect, rather than increased parasite load. Nest box cleaning had no effect on measured variables in case of Red-footed Falcons and Jackdaws. Colonial breeding of Kestrels, the only species to react to nest-box cleaning, is rare and is probably a consequence of extreme nest-site shortage in our study site. We conclude that Kestrels are not adapted to interpret the information carried by pellets and prey-remnants in colony nest-boxes.

The Red-footed Falcon is a facultatively colonial species that exploits rookeries, artificial nest-box colonies and solitary corvid nests for breeding. Moreover, the remain gregarious in the post breeding period using communal roost sites prior to migration. We developed and implemented a survey protocol to allow to precisely estimate the number of breeding pairs in all three breeding types and to assess large scale spatio-temporal changes in roost site usage. Our results show that the lowest number of breeding pairs (558) was in 2006. However, in 2014 the number of pairs showed a two fold increase, mainly due to a large scale nest-box programme implemented in the past decade. We identified a total of 105 roost sites throughout the country. The number of birds peaked in the second week of September in the past 10 years. We formulate a recommendation to maintain population monitoring efficiency by reducing the frequency of full surveys to 5 years and using designated study areas to control for temporal trends in between.

The Red-footed Falcon population in Voivodina shows a considerable decrease on a large temporal scale, however due to recent conservation measures, it seems to be stable in the past six years. Here I present the history of population estimates and results of partial surveys that have been carried out since 1909. I also show the details and results of conservation efforts recently implemented in the region. Recovery records of individually colour ringed birds indicate that the population breeding in northern Serbia is an integral part of the Carpathian Basin population and thus conservation management should be coordinated within a framework of international cooperation.