Effects of the risk of competition and predation on large secondary cavity breeders

Abstract

The effects of competition and risk of predation on secondary cavity breeders were examined between the 2008 and 2009 breeding seasons using an experimental design manipulating two nest entrance sizes (large entrances allowed Barn Owls (Tyto alba) to enter, while the small entrances excluded them). During the 2009 breeding season, the entrance sizes of nest boxes were exchanged, so that if during one year a nest box in a particular location had a small entrance, the second year it had a large entrance and vice versa. Barn Owls and Eurasian Kestrels (Falco tinnunculus) occupied 67.3 and 17.3%, respectively, of large entrance nest boxes. Significantly more Jackdaws (Corvus monedula), House Sparrows (Passer domesticus) and Scops Owls (Otus scops) bred in nest boxes with small than with large entrances. After nest box entrance sizes were exchanged, Barn Owls and smaller species did not breed in the same nest boxes with the new entrance size. Jackdaws probably did not breed in large entrance nest boxes due both to exploitation competition (Barn Owls and Eurasian Kestrels occupied the majority of large entrance nest boxes), and may also have avoided empty nest boxes because of the risk of interference competition; whereas smaller species may have also avoided large entrance nest boxes due to risk of predation.

The Habitat-Trees experiment: using exotic tree species as new microhabitats for the native fauna

“…In contrast with what was observed by Charter et al (2013), Parus sp. were able to breed in nests with wider entrances even in the presence of larger-sized competitors, possibly because the abundance of the latter was too low to generate interspecific competition (Robles et al 2012).…”

“…Passerines are known to select for cavities in living trees (Robles et al 2011), and thermoregulatory advantages are a likely cause of this selection (Remm et al 2006). However, cavities were not used for long periods, possibly because of the frequent displacement of the plugs that delimited the entrance, increasing the risk of predation (Charter et al 2010). Furthermore, the enlargement of the entrance was often associated with the soaking of the nest, another factor decreasing the cavity suitability (Wesolowski et al 2002).…”

Nest-site competition between invasive and native cavity nesting birds and its implication for conservation

“…House sparrows are the most common and opportunistic secondary-cavity breeders in Israel, having occupied many different nest boxes types throughout Israel in the past (Charter et al, 2010(Charter et al, , 2011(Charter et al, , 2010b. House sparrows have bred successfully in large numbers in similar nest boxes in the same study areas in the past (Orchan, 2007) and we therefore think that there should have been more pairs breeding.…”

“…The internal height of nest boxes from the bottom of the nest was similar in all cases. The large-entrance nest boxes were similar to the natural native Syrian woodpecker (Dendrocopos syriacus) holes (the primary cavity excavator of the site), which can be accessed by both alien species and also two large common native cavity breeders species (hoopoe and Scops owls; Charter et al, 2008;Charter et al, 2010b). Small-entrance nest boxes (39 mm entrance) were placed that prevented the larger alien species and the two larger native cavity breeders (hoopoe and Scops owls) access to the nest but allowed the two most common native cavity breeders, the smaller native great tits and house sparrows, to enter (Charter et al, 2010a).…”

Nest box design for the study of diurnal raptors and owls is still an overlooked point in ecological, evolutionary and conservation studies: a review

“…While larger-bodied species require large entrances, smaller individuals or species may prefer to breed in nest boxes with small entrance holes to reduce risks related to predation or competition. The dimensions of the nest box characteristics apparently influence interactions between Eurasian Kestrels and Barn Owls in Israel (Charter et al 2007(Charter et al , 2010b, between Tawny Owls and Tengmalm's Owls in southern Finland and Spain (Solonen 1993;Ló pez et al 2010), between Tengmalm's Owls, Ural Owls (S. uralensis) and Eagle Owls (Bubo bubo) in western Finland (Hakkarainen and Korpimäki 1996), between Barn Owls and Tawny Owls in northeast England (Petty et al 1994), and between Eurasian Kestrels and Tawny Owls in Rome (D. Costantini and G. Dell'Omo, personal communication). In western Finland, Tengmalm's Owls mostly avoided breeding in the largest boxes (internal diameter 26-35 cm, entrance hole 15-18 cm) probably because Ural Owls could have entered them and physically removed the Tengmalm's Owls (Hakkarainen and Korpimäki 1996).…”