Leucocytozoon Infection Does Not Influence the Survival of Boreal Owl Aegolius funereus Nestlings.

Leucocytozoon infection has been observed to impact the reproductive ecology and physiology of avian hosts, but its influence on nestling survival remains unclear. We investigated the effect of Leucocytozoon infection intensity, determined through triplicate PCR sample analyses, on the survival of 256 boreal owl (Aegolius funereus) nestlings during an 8-yr study. Contrary to our expectations, the survival probability of boreal owl nestlings was not influenced by their Leucocytozoon infection intensity. Nestling age and Leucocytozoon infection intensity in male and female parents also did not impact nestling survival. Instead, food abundance and hatching order were the key factors influencing nestling survival. Additionally, we observed a significantly higher Leucocytozoon infection intensity in male parents compared to female parents and nestlings. We suggest a distinct division of parental roles may lead females and nestlings staying within the nest boxes (cavities) to experience lower exposure to potential vectors transmitting blood parasites than their male counterparts. Our study shows that Leucocytozoon disease may not be lethal for boreal owl chicks, exhibiting a below-average infection intensity compared to their male parents.

La infección por Leucocytozoon no influye en la supervivencia de los polluelos de mochuelo boreal Aegolius funereus. Se ha observado que la infección por Leucocytozoon afecta la ecología y fisiología reproductiva de las aves hospedadoras, pero su influencia en la supervivencia de los polluelos aún no está completamente determinada. Se investigó el efecto de la intensidad de la infección por Leucocytozoon, determinada mediante análisis de muestras de PCR por triplicado, sobre la supervivencia de 256 polluelos de mochuelo boreal (Aegolius funereus) durante un estudio de ocho años. Contrariamente a nuestras expectativas, la probabilidad de supervivencia de los polluelos de mochuelo boreal no se vio influenciada por la intensidad de la infección por Leucocytozoon. La edad de los polluelos y la intensidad de la infección por Leucocytozoon en los padres machos y hembras tampoco afectaron la supervivencia de los polluelos. En cambio, la abundancia de alimento y el orden de eclosión fueron los principales factores que influyeron en la supervivencia de los polluelos. Además, se observó una intensidad de infección por Leucocytozoon significativamente mayor en los padres machos en comparación con las hembras y los polluelos. Se sugiere que una clara división de los roles parentales puede llevar a que las hembras y los polluelos que permanecen dentro de las cajas nido (cavidades) experimenten una menor exposición a vectores potenciales que transmitan parásitos sanguíneos en comparación con los individuos adultos masculinos. Nuestro estudio muestra que la enfermedad de Leucocytozoon puede no ser letal para los polluelos de mochuelo boreal, ya que exhiben una intensidad de infección por debajo del promedio en comparación con sus padres machos.

Forest structure determines nest box use by Central European boreal owls.

Nest boxes represent a popular tool to support secondary cavity-nesting species. Surprisingly, the benefits and limitations of nest boxes for target species in different environments are poorly understood. We performed a 3-years experimental study in two different Central European forests to evaluate nest box use and breeding performance of boreal owl (Aegolius funereus) - a species well known for its readiness to occupy nest boxes. Based on territorial vocalisation, two boreal owl populations 200 km apart were similarly abundant in their environments. However, only the boreal owl population in young restored Norway (Picea abies) and blue (Picea pungens) spruce-dominated forests on mountain plateaus readily occupied nest boxes with the occupancy reaching 8-15%. Nest boxes lost their supporting function for the boreal owl in mature Scots pine (Pinus sylvestris)-dominated forests in the lowland, where the nest box occupancy reached 0-1%. As a result, the population of boreal owls that used nest boxes in the young restored forests produced 10 times more fledglings than the population inhabiting mature Scots pine forests. We explain the differences by the contrasting availability of natural tree cavities between the two study areas being much higher in mature Scots pine forests. For the first time, this study documents differences in nest box use despite similar food availability and population size of the target species. The study provides the findings-related recommendations for deploying nest boxes for boreal owls and points out a general lack of practical guides.

Large-scale spatial patterns of small-mammal communities in the Mediterranean region revealed by Barn owl diet.

Due to mainly opportunistic hunting behaviour of Barn owl can be its diet composition used for assessing local structure of small-mammal community. We evaluated the structure of small-mammal communities in the Mediterranean region by analysing Barn owl diet using own pellets and literature data (85 localities comprising 182,343 prey individuals). Contrary to widely accepted macroecological theory, we found a latitudinal increase of small-mammal alpha diversity, a less distinct west-east increase and lower diversity on islands. The mean prey weight decreased with increasing latitude, while on islands it decreased with increasing island area. The mean prey weight on islands was further negatively affected by mean land modification by human and positively affected by its range. The diet diversity on islands was not affected either by island area or its distance from the mainland. Its composition largely conformed to the main pattern pronounced over whole the region: an unexpected homogeneity of small-mammal community structure. Despite high beta diversity and large between-sample variation in species composition, Crocidura (+ Suncus etruscus) and murids (Apodemus, Mus, Rattus, in marginal regions partly replaced by gerbillids, Meriones or Microtus) composed more than 90% of owl prey in 92% of samples. Peak abundances of these widespread species are associated with a dynamic mosaic of dense patches of sparse herb vegetation and evergreen sclerophyllous shrublands interspersing areas of human activity, the dominant habitat of the inner Mediterranean and richest food resource for foraging Barn owls. The respective small-mammal species can be looked upon as invasive elements accompanying large scale human colonization of the region since the Neolithic and replacing original island biota. Our study documented that desertification of the Mediterranean played an important role in shaping inverse latitudinal gradient in diversity of small-mammals that contradicts to widely accepted mecroecological theory.

Home range size of Tengmalm's owl during breeding in Central Europe is determined by prey abundance.

Animal home ranges typically characterized by their size, shape and a given time interval can be affected by many different biotic and abiotic factors. However, despite the fact that many studies have addressed home ranges, our knowledge of the factors influencing the size of area occupied by different animals is, in many cases, still quite poor, especially among raptors. Using radio-telemetry (VHF; 2.1 g tail-mounted tags) we studied movements of 20 Tengmalm's owl (Aegolius funereus) males during the breeding season in a mountain area of Central Europe (the Czech Republic, the Ore Mountains: 50° 40' N, 13° 35' E) between years 2006-2010, determined their average hunting home range size and explored what factors affected the size of home range utilised. The mean breeding home range size calculated according to 95% fixed kernel density estimator was 190.7 ± 65.7 ha (± SD) with a median value of 187.1 ha. Home range size was affected by prey abundance, presence or absence of polygyny, the number of fledglings, and weather conditions. Home range size increased with decreasing prey abundance. Polygynously mated males had overall larger home range than those mated monogamously, and individuals with more fledged young possessed larger home range compared to those with fewer raised fledglings. Finally, we found that home ranges recorded during harsh weather (nights with strong wind speed and/or heavy rain) were smaller in size than those registered during better weather. Overall, the results provide novel insights into what factors may influence home range size and emphasize the prey abundance as a key factor for breeding dynamics in Tengmalm's owl.

A Webcast of Bird Nesting as a State-of-the-Art Citizen Science.

The quality of people's knowledge of nature has always had a significant influence on their approach to wildlife and nature conservation. However, direct interactions of people with nature are greatly limited nowadays, especially because of urbanization and modern lifestyles. As a result, our isolation from the natural world has been growing. Here, we present an example of a state-of-the-art Citizen Science project with its educational, scientific, and popularizing benefits. We conclude that modern media and new forms of education offer an effective opportunity for inspiring children and others to have fun learning to act like scientists. This approach provides broad opportunities for developing the hitherto neglected educational potential of Citizen Science.

Factors Affecting Growth of Tengmalm's Owl (Aegolius funereus) Nestlings: Prey Abundance, Sex and Hatching Order.

In altricial birds, energy supply during growth is a major predictor of the physical condition and survival prospects of fledglings. A number of experimental studies have shown that nestling body mass and wing length can vary with particular extrinsic factors, but between-year observational data on this topic are scarce. Based on a seven-year observational study in a central European Tengmalm's owl population we examine the effect of year, brood size, hatching order, and sex on nestling body mass and wing length, as well as the effect of prey abundance on parameters of growth curve. We found that nestling body mass varied among years, and parameters of growth curve, i.e. growth rate and inflection point in particular, increased with increasing abundance of the owl's main prey (Apodemus mice, Microtus voles), and pooled prey abundance (Apodemus mice, Microtus voles, and Sorex shrews). Furthermore, nestling body mass varied with hatching order and between sexes being larger for females and for the first-hatched brood mates. Brood size had no effect on nestling body mass. Simultaneously, we found no effect of year, brood size, hatching order, or sex on the wing length of nestlings. Our findings suggest that in this temperate owl population, nestling body mass is more sensitive to prey abundance than is wing length. The latter is probably more limited by the physiology of the species.

Factors affecting the duration of nestling period and fledging order in Tengmalm's owl (Aegolius funereus): effect of wing length and hatching sequence.

In altricial birds, the nestling period is an important part of the breeding phase because the juveniles may spend quite a long time in the nest, with associated high energy costs for the parents. The length of the nestling period can be variable and its duration may be influenced by both biotic and abiotic factors; however, studies of this have mostly been undertaken on passerine birds. We studied individual duration of nestling period of 98 Tengmalm's owl chicks (Aegolius funereus) at 27 nests during five breeding seasons using a camera and chip system and radio-telemetry. We found the nestlings stayed in the nest box for 27 - 38 days from hatching (mean ± SD, 32.4 ± 2.2 days). The individual duration of nestling period was negatively related to wing length, but no formally significant effect was found for body weight, sex, prey availability and/or weather conditions. The fledging sequence of individual nestlings was primarily related to hatching order; no relationship with wing length and/or other factors was found in this case. We suggest the length of wing is the most important measure of body condition and individual quality in Tengmalm's owl young determining the duration of the nestling period. Other differences from passerines (e.g., the lack of effect of weather or prey availability on nestling period) are considered likely to be due to different life-history traits, in particular different food habits and nesting sites and greater risk of nest predation among passerines.

Different temperature and cooling patterns at the blunt and sharp egg poles reflect the arrangement of eggs in an avian clutch.

Incubation is an energetically demanding process during which birds apply heat to their eggs to ensure embryonic development. Parent behaviours such as egg turning and exchanging the outer and central eggs in the nest cup affect the amount of heat lost to the environment from individual eggs. Little is known, however, about whether and how egg surface temperature and cooling rates vary among the different areas of an egg and how the arrangement of eggs within the clutch influences heat loss. We performed laboratory (using Japanese quail eggs) and field (with northern lapwing eggs) experiments using infrared imaging to assess the temperature and cooling patterns of heated eggs and clutches. We found that (i) the sharp poles of individual quail eggs warmed to a higher egg surface temperature than did the blunt poles, resulting in faster cooling at the sharp poles compared to the blunt poles; (ii) both quail and lapwing clutches with the sharp poles oriented towards the clutch centre (arranged clutches) maintained higher temperatures over the central part of the clutch than occurred in those clutches where most of the sharp egg poles were oriented towards the exterior (scattered clutches); and (iii) the arranged clutches of both quail and lapwing showed slower cooling rates at both the inner and outer clutch positions than did the respective parts of scattered clutches. Our results demonstrate that egg surface temperature and cooling rates differ between the sharp and blunt poles of the egg and that the orientation of individual eggs within the nest cup can significantly affect cooling of the clutch as a whole. We suggest that birds can arrange their eggs within the nest cup to optimise thermoregulation of the clutch.

Perching of Tengmalm's owl (Aegolius funereus) nestlings at the nest box entrance: effect of time of the day, age, wing length and body weight.

The behaviour of the nestlings of nocturnal cavity-nesting species has relatively rarely been studied in detail because of problems connected with use of the technical devices required to provide long-term monitoring of individuals. However, long-term observation of nestling behaviour is crucial in order to identify different types of behaviour which may be caused by sibling competition at the end of nesting period. We studied behaviour of 43 Tengmalm's owl (Aegolius funereus) nestlings at 14 nests using a camera and a chip system. The nestlings perched at the nest box entrance from an average age of 28 days from hatching (range 24-34 days) until fledging, spending around 2 hours per day here in total, in periods ranging from a few seconds to 147 min (7.6±10.9 min, mean ± SD). We found that individual duration of perching at the nest box entrance was significantly influenced by nestlings' age and wing length and that the duration of perching at the nest box entrance significantly decreased with time of night. However, during daylight hours, time of day had no effect on either probability or duration of nestlings' perching. We suggest daylight perching at the nest box entrance results from nestlings' preparation for fledging, while individuals perching here during the night may gain an advantageous position for obtaining food from the parents; another possibility at all times of day is that nestlings can reaffirm their social dominance status by monopolizing the nest box entrance.

Dark or short nights: differential latitudinal constraints in nestling provisioning patterns of a nocturnally hunting bird species.

In diurnal bird species, individuals breeding at high latitudes have larger broods than at lower latitudes, which has been linked to differences in the daily time available for foraging. However, it remains unclear how latitude is linked with parental investment in nocturnal species. Here, we investigate nestling provisioning rates of male Tengmalm's owls in two populations at different latitudes (Czech Republic 50 °N; Finland 63 °N) with the help of cameras integrated into nest boxes. Clutch sizes were smaller in the Czech population (CZ: 5.1 ± 0.1; FIN: 6.6 ± 0.1), but given the higher nestling mortality in the Finnish population, the number of fledglings did not differ between the two populations (CZ: 3.5 ± 0.3; FIN: 3.9 ± 0.2). Nestling provisioning patterns varied within days, over the reproductive season and between the two sites. Males delivered most food at dusk and dawn, having peak delivery rates at sun angles of -11° to -15° at both sites, and males increased the prey delivery rates with higher nestling requirements. Given the longer nights during summer in the Czech Republic compared to Finland, Czech males only showed a small shift in their delivery peak during the night from -17° in April to -14° in July. In contrast, Finnish males shifted their peak of prey delivery from -11° in April to -1° in July. Consequently, Czech males had a longer hunting time per night around midsummer when feeding young (360 min) than Finnish males (270 min). This suggests that nocturnal owl species in northern populations are constrained by the short nights during the breeding season, which can limit the number of young they can raise. Moreover, owls in northern populations are additionally constrained through the unpredictable changes in food availability between years, and both these factors are likely to influence the reproductive investment between populations.