This chapter gives an overview of the embryonic development and morphological characteristics of the Little Owl. We first look at how the egg develops, with special attention paid to the temporary asymmetric ears, then zoom in on owlet development as they grow and the plumage of adult birds and how molt takes place. The eyes are special and the species has retinal cells similar to diurnal birds of prey. While Little Owls can differentiate several colors, the species does not see infra-red rays. It has an auditory sensitivity to locate small rodents with an accuracy of up to 1%. The bill is yellowish and its color functions as a signal for the fitness of both juveniles and adults. The Little Owl has differential biometrical measures (such as length of wing, tail, tarsus) according to the subspecies or according to the sex (such as weight - females are heavier close to the breeding time). We finally examine the voice. The species has a large vocal repertoire, including 40 acoustic signals and combinations with regional specificities. The chapter concludes with specific characteristics for flight and the anatomy.

Little Owls have been shown to be directly and indirectly affected by habitat loss, vehicle collisions, limited availability of nest and roosting sites, pesticides (i.e., secondary poisoning) and heavy metals, entrapment in anthropogenic structures (i.e., hollow metal power poles and chimneys, and drowning in water troughs), predators and weather. They are susceptible to parasites, diseases and injuries too. While the Little Owl has co-evolved with a few of these (e.g., weather, predators, diseases, parasites), anthropogenic activities have substantially altered the landscape within which Little Owls exist(ed). When the population grows and owl densities become higher, density-dependent processes take place and serve to stabilise the population. In a metapopulation context, as populations become increasingly small, immigration helps to support them, extending the survival time of these population clusters. The mating system hypothesis, which predicts that the sex that establishes the territory should disperse shorter distances, was studied using the EURING data set containing 108 444 observations of ringing, re-capture and recovery data for 59 743 unique ringed birds. Little Owls ringed as young and recovered at least one year later dispersed on average 14.69 km for females, 6.47 km for males and 11.61 km for birds with unknown sex for live re-captures. Birds ringed as adults and then later recovered dispersed 2.33 km for females, 2.45 km for males and 2.42 km for birds with unknown sex for live re-captures.

The framework of this book reflects the complexity of the situation of the species at different scales. To position the Little Owl in the cultural context we look at the history and cultural traditions connected to the species. We describe the taxonomy and subspecies to settle some taxonomic discussions of the species based upon major genetic, morphological and biogeographical findings. The distribution of the different subspecies and recent population estimates for the Western Palearctic are given to illustrate the geographic diversity. The habitat is described and its relationships with the species. Food as principle biotic factor delivers the crucial energy input for the birds. Abiotic factors such as breeding cavities and perches show their importance for breeding and foraging efficiency to minimize the energetic cost. Next we focus on the breeding season, discussing clutch size, hatching and fledging success in relation to the age of the birds. We then describe behavior mainly based upon two decades of webcam observations. Next we zoom in on limiting factors that influence populations in a given geographic environment, e.g., immigration, re-introduction or supplementation, and mechanisms of interaction between local populations, such as migration, meta-populations and sinks/sources. After describing the main causes for declines in the species, we summarize knowledge into a conservation and management strategy. We conclude this chapter with an overview of the key points raised, with an overview of the most important open questions and suggestions for future studies.

New media such as internet-connected cameras in nestboxes can yield infra-red images in the dark leading to new insights and knowledge. Substantial new information has become available from the groundbreaking webcam project of Vogelbescherming Nederland Beleef de Lente that started in 2007 and continues to this day. Volunteers select video clips revealing as yet undiscovered remarkable behavior over 14 entire breeding seasons, day and night, from courtship to egg-laying, to the fledging of the young. Due to simpler and cheaper technology, more and more people have decided to install such cameras in their nestboxed which is expected to yield even more new knowledge in the future, opening unprecedented opportunities for citizen science. This chapter is complemented by a lot of information from the long-term research of Van Harxen and Stroeken (from 1986) in their study area in Southeast Achterhoek in the Netherlands.

This chapter covers the entire Little Owl breeding cycle. The breeding season is obviously a critically important period during which reproduction can be influenced by many different factors, such as weather, food, habitat, density, geographical location and parental experience. The season begins in January or February with the affirmation of territorial boundaries and onset of courtship. The Little Owl does not have high a productivity due to very few replacement clutches, moderate fledging success and relatively high egg failure. According to the mortality rate of adults and juveniles, each pair should produce between 1.7 and 2.34 fledged young per year to compensate mortality and actually most of the long-term breeding studies across Europe show results ranging between both values. Analysis of consistently organized long-term demographic data has enhanced our understanding of Little Owl population dynamics. Further, this demographic data has been linked to specific habitat conditions at the nest site, home range and landscape scales. We offer clarification of the terminology related to nesting success and reproduction due to its importance in providing an accurate and consistent foundation for the data that will be used to assess the reproductive performance of the owls, as well in long-term monitoring of status and trends.

The Little Owl has a generalist diet and takes a high diversity of small prey. It eats a range of small-sized prey across its entire distribution area. The diet varies with the season and the geographical area. From north to south and from winter to summer, an increase in the numbers of insects in the diet has been observed. However, small mammals remain the key prey category by biomass and energetic yield, contributing significantly to the ecology and welfare of the species. For insect-eating owl species it is difficult to get a true picture of its diet by only studying its pellets or prey remains in nestboxes, because they catch lots of prey, the remains of which are hard to find and identify in pellets. We present their relative proportion. In this chapter we look at this prey diversity through time and space, and focus on the hunting method of the owl, as well as caching behavior in larders. We offer a thorough review of the owl’s diet and individual prey species, with attention given to the importance of micromammals. Pellet contents are described in detail and comprehensive results of camera-observed breeding seasons are presented, principally stemming from our own research over 17 breeding seasons by camera observation in 2002-2020, totaling 34 916 prey items.

This chapter presents a brief overview of the status of and threats to the Little Owl. We then offer a conservation strategy for the owl that involves five critical success factors: Knowledge, Limiting Factors, Evolution of Landscape Conditions, Legislation and Policies, and People. Thereafter, we describe four main drivers to implement this strategy, focused on Monitoring, Management, Standardized Methodologies and Data Management. The long-term conservation of the Little Owl is complicated, as the species is largely linked to an agriculturally dominated landscape. This landscape condition can change rapidly and significantly due to human demographics, and changes in policies and management. The conservation strategy described in this chapter requires a multiscale, multidisciplinary approach, with collaboration between different stakeholders (conservationists, scientists, different authorities, farmers) and additional research into the ecology of the species. This strategy must be applied at different levels: local, regional, national and international. We encourage people involved in this conservation strategy to work broadly, openly and to freely co-ordinate on issues, data, and management efforts that will benefit the broader array of species and environments of which the Little Owl is a part.