Demography, breeding success and effects of nest type in artificial colonies of Red-footed Falcons and allies

Abstract

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.

History and current status of Red-footed Falcon population size and conservation activities in Voivodina

“…We have erected over 350 nest-boxes in various locations, primarily choosing sites that had historic breeding records, or were pin-pointed by landscape scale habitat modelling as suitable breeding sites (Fehérvári et al 2012). Predominantly we used 2 nest-box designs; 1) the box most often used in Hungary (see Kotymán et al 2015): 2.C.B. box, and 2) a relatively large box that in shape resembles the previous type, however with approx.…”

Provisioning nest material for Rooks; a potential tool for conservation management

“…This, coupled with altered land use of the past decades resulted in a dramatic decline of the rook population (Solt 2008), leaving suitable foraging habitats without nesting sites for the Red-footed Falcons in the Carpathian Basin. An over decade long country-wide nest-box scheme has temporarily resolved this resource shortage, however, sustainability of these breeding sites remains to be improved , Kotymán et al 2015. Rooks are gene ralist feeders and build their own nests, hence supplementing breeding facilities, or foraging stations are unlikely to have a substantial effect on local or regional demography where natural foraging areas are still available (Olea & Baglione 2008).…”

Species specific effect of nest-box cleaning on settlement selection decisions in an artificial colony system

“…A takarított ládákban a vörös vércse tojások szignifikánsan magasabb aránya eredményezett sikeresen kirepülő fiókát, mint a takarítatlan ládákban (Roulin 1998, 1999, Liker et al 2001, Kaľavský & Pospíšilová 2010. In general, occupation rate and breeding success was relatively low in the study year (see Kotymán et al 2015), presumably due to above ave rage precipitation frequency and quantity throughout the breeding season. We used semi-closed nest-boxes providing shelter against rainfall, however, the large opening on the front does not completely keep the clutch dry (pers.…”

“…The study was carried out in 2013 at an artificial colony system located in the Vásárhe-lyi Plains, Hungary (see Kotymán et al 2015 for details). Here, a total of 251 nest-boxes were available in 4 larger colonies, several smaller clusters and as platforms for solitary breeding.…”