Win – and stay, but not too long: cavity selection by Boreal Owls to minimize nest predation by Pine Marten

Site fidelity after successful nesting and site shift after nest predation (win–stay, lose–shift) is a well-documented adaptation to spatially heterogeneous and temporally auto-correlated predation risk. However, site shift even after a successful nesting (win–shift) may become a better tactic than site fidelity (win–stay), if a successful nest site becomes more risky until the next nesting opportunity, and if new low-risk nest sites regularly appear. Correspondingly, selecting a new non-used nest site may become a better tactic than selecting one previously used successfully by a conspecific. I studied this dynamic by focusing on nest cavities that may be available for many years, and using nest boxes to allow an experimental design. At localities where Boreal Owls (Aegolius funereus) had nested successfully, a dyad of nest boxes was made available each year, one box in the original nest tree and one in a new tree for the season, each containing either old nest material from the successful nesting or new wood shavings. Boreal owls were more likely to select the box in the new tree when more years had elapsed since the successful nesting and since a box was installed in the original nest tree, independent of box content. The pattern of selection differed between young and old individuals for males, but not females. Young males based their selection of nest tree mainly on box content, while old males based it on time elapsed since the successful nesting in the original nest tree and how long a box had been present there. The probability of depredation of Boreal Owl nests by Pine Marten (Martes martes) has previously been found to increase with cavity age and number of nesting seasons elapsed since the previous successful nesting. This pattern of nest predation thus predicted the pattern of nest site selection found.

Monopis jussii, a new species (Lepidoptera, Tineidae) inhabiting nests of the Boreal owl (Aegolius funereus)

Monopis jussii Kaila, Mutanen, Huemer, Karsholt & Autto, sp. nov. (Lepidoptera, Tineidae) is described as a new species. It is closely related to the widespread and common M. laevigella ([Denis & Schiffermüller], 1775), but differs in its distinct COI DNA barcode sequences, four examined nuclear loci as well as details in forewing coloration and pattern. Most reared specimens of M. jussii have emerged from the nest remnants of the Boreal owl (Aegolius funereus (Linnaeus, 1758)), but also nests of the Ural owl (Strix uralensis Pallas, 1771) and the Great tit (Parus major Linnaeus, 1758) have been observed as suitable habitats. Based on the present knowledge, the new species has a boreo-montane distribution as it is recorded only from northern Europe and the Alps. Several extensive rearing experiments from Strix spp. nest remnants from southern Finland did not produce any M. jussii, but thousands of M. laevigella, suggesting that the species is lacking in the area or, more unlikely, that the nest of these owl species do not serve as good habitat for the new species. This unexpected species discovery highlights, once again, the usefulness of DNA barcoding in revealing the cryptic layers of biodiversity. To serve stability we select a neotype for Tinea laevigella [Denis & Schiffermüller], 1775, and discuss the complicated synonymy and nomenclature of this species.

Boreal Owl (Aegolius funereus) and Northern Saw-whet Owl (Aegolius acadicus) breeding records in managed boreal forests

During the 2016 breeding season we monitored 169 nest boxes suitable for Boreal Owl (Aegolius funereus) and Northern Saw-whet Owl (Aegolius acadicus) in high-latitude (>55°N) boreal forests of northwestern Alberta affected by partial logging. Despite the large number of boxes deployed, the number of boxes used by Boreal and Northern Saw-whet Owls was small. Boreal Owls used nest boxes (n = 4) in conifer-dominated stands with three being in uncut blocks and the other in a 50% green tree retention cut-block. In contrast, Northern Saw-whet Owls used boxes (n = 4) in a broader range of cover types, breeding in boxes placed in stands with at least 20% post-harvest tree retention. Although both species successfully bred in the same landscape, Boreal Owls produced fewer eggs (mean = 2.5) and raised fewer young (mean = 0.5) than Northern Saw-whet Owls (5 and 2.25, respectively). Furthermore, our observed Boreal Owl egg production was lower than has been found for the same species nesting in nest boxes in different regions or forest types. In contrast, breeding parameters of Northern Saw-whet Owls were similar to that found in nest boxes in the eastern boreal region of Canada and in the southern part of its range.

New Data on Phylogeography of the Boreal Owl Aegolius funereus in Eurasia

In the article the research’s results of phylogeography, genetic diversity, genetic structure and demographic characteristics of the Boreal Owl population in Eurasia are given. The first domain of control region of mtDNA is used as a genetic marker. The sample size was 59 specimens. The population of Boreal Owl is characteristic of high genetic diversity and it has signs of rapid expansion in the past as revealed by analysis of CR1 mtDNA polymorphism. Genetic differentiation between birds from the west and the east part of the species range is shown. The level of found population genetic differentiation isn’t high that can be explained by gene flow in the past and possible at the present time. We didn’t reveal any signs of genetic differentiation for Boreal Owl population according to subspecies (between A. f. funereus and A. f. pallens) which are distinguished for the studying area.

Infestation parameters for chewing lice (Phthiraptera: Amblycera, Ischnocera) infesting owls (Aves: Strigidae, Tytonidae) in Manitoba, Canada

Eleven of the 12 species of owls (Aves: Strigidae, Tytonidae) known to occur in Manitoba, Canada, were examined for chewing lice (Phthiraptera: Amblycera, Ischnocera) from 1976 to 2015: barn owl (Tyto alba (Scopoli); Aves: Tytonidae) (n = 2), snowy owl (Bubo scandiacus (Linnaeus); Aves: Strigidae) (n = 77), great horned owl (Bubo virginianus (Gmelin); Aves: Strigidae) (n = 262), great grey owl (Strix nebulosa Förster; Aves: Strigidae) (n = 142), barred owl (Strix varia Barton; Aves: Strigidae) (n = 10), northern hawk owl (Surnia ulula (Linnaeus); Aves: Strigidae) (n = 18), short-eared owl (Asio flammeus (Pontoppidan); Aves: Strigidae) (n = 74), long-eared owl (Asio otus (Linnaeus); Aves: Strigidae) (n = 67), eastern screech owl (Megascops aslo (Linnaeus); Aves: Strigidae) (n = 59), boreal owl (Aegolius funereus (Linnaeus); Aves: Strigidae) (n = 47), and northern saw-whet owl (Aegolius acadicus (Gmelin); Aves: Strigidae) (n = 44), a total of 802 owls. No lice were found infesting barn owl (Tyto alba (Scopoli); Aves: Tytonidae) or eastern screech owl (Megascops asio (Linnaeus); Aves: Strigidae). We collected a total of 113 810 lice of 12 species: Kurodaia Uchida (Phthiraptera: Menoponidae) – three species; and Strigiphilus Mjöberg (Phthiraptera: Philopteridae) – nine species. Overall prevalence of infestation ranged from 10.0% to 88.9%. Mean intensity for total lice ranged from 22.4 to 506.5. Infestation parameters for each louse–host combination are provided; prevalence and mean intensity were not related for louse–host species combinations. Distribution of louse infestations was highly aggregated. In all louse–host combinations but one, either females were more prevalent than males or there was no significant deviation from 50:50. Male Strigiphilus ceblebrachys Denny significantly outnumbered females in snowy owls. There was a tendency for louse species to co-occur on the same host specimen. Where sample sizes for owls were large enough, no seasonal patterns in abundance of lice were detected.

Diet of boreal owl (Aegolius funereus) in lowlands of north-eastern Poland

Although studies on many owl species diets are common, there are only scarce data on the diet of the boreal owl from the lowlands of Eastern Europe. We have therefore studied its diet in one of the most important Polish population areas, the Knyszyńska Forest (north-eastern Poland). Pellets were gathered between February and June in 2006, 2012–2016 from tree hollows and the ground underneath. Altogether 178 pellets and six sets of pellet fragments were collected from 19 different sites. Eight mammal and eight bird species were identified among the 213 prey items found in the gathered material. Small mammals dominated, both in prey number (88.3%) and biomass (85.1%). Bank vole proved to be the main prey (over 40% of prey numbers), while Microtus voles (27.3%), small passerine birds (11.7%) and shrews (7.5%) were important alternative prey. Diet range proved to be similar to other sites in Europe.