The impact of vegetation characteristics and prey availability on breeding habitat use and diet of Little Owls Athene noctua in Central European farmland

Figures & data

Figure 1 Distribution of study localities, Little Owl nest‐sites, and insect‐trapping sites in the study area, western Bohemia, Czech Republic.

Table 1. Weight, frequency and biomass of each component in the diet of Little Owls, based on pellet analysis.

	Weight	Number	Biomass
Prey species	g	n	%	B	%
Microtus arvalis	20	219	24.4	4380	69.1
Apodemus sp.	25	19	2.1	475	7.5
Mus musculus	19	6	0.7	114	1.8
Crocidura leucodon	12	18	2.0	216	3.4
Micromys minutus	19	11	1.2	209	3.3
Sorex minutus	4	2	0.2	8	0.1
Sorex araneus	9	2	0.2	18	0.3
Undetermined Rodentia	19	38	4.2	722	11.4
Mammalia, total		315	35.1	6142	96.8
Passer sp.	27	2	0.2	54	0.9
Carduelis chloris	30	1	0.1	30	0.5
Fringilla coelebs	25	1	0.1	25	0.4
Phoenicurus sp.	16	1	0.1	16	0.3
Aves, total		5	0.6	125	2.0
Insecta	0.003–0.870	578	64.4	75.8	1.2
Total		898	100.0	6342.8	100.0
g, average weight of prey animals in grams; n, number of items; B, prey biomass in grams.

Figure 2 Projection scores of the main components of the diet of Little Owls in western Bohemia expressed as numbers (principle component analysis, I and II axis explained 72.4 % of total variation). Horizontal axis, I; vertical axis, II.

Table 2. Comparison of the composition of trapped insects and Little Owl insect diet composition (χ²test).

	Insect trappings	Little Owl diet
Prey species	n	%	Meadows	%	Cornfields	%	n	%	P(overall)	P(meadows)	P(cornfields)
Poecilus cupreus (I)*	2000	81.9	519	79.4	1481	82.9	3	1.1	<0.001	<0.001	<0.001
Pterostichus melanarius (N)*	212	8.7	39	6.0	173	9.7	205	75.4	<0.001	<0.001	0.244
Pseudoophonus rufipes (N)*	122	5.0	44	6.7	78	4.4	0	0	0.001	<0.001	<0.001
Carabus granulatus (I)	45	1.8	7	1.1	38	2.1	35	12.9	0.052	0.001	0.803
Oodes helopioides (N)	19	0.8	15	2.3	4	0.2	0	0	0.598	0.002	0.103
Nebria brevicollis (N)	16	0.7	15	2.3	1	0.1	1	0.4	0.888	0.006	1.000
Abax parallelepipedus (N)	13	0.5	6	0.9	7	0.4	1	0.4	0.963	0.143	0.106
Agonum muelleri (D)	11	0.5	8	1.2	3	0.2	1	0.4	0.965	0.069	0.465
Carabus nemoralis (I)	3	0.1	1	0.2	2	0.1	26	9.6	0.575	<0.001	<0.001
The significance level after Bonferroni correction was set at 0.006; overall significant differences are marked with an asterisk; N, nocturnal activity; D, diurnal activity; I, diurnal and crepuscular activity.

Table 3. Factors affecting the availability of insect prey on Little Owl hunting areas and the proportion of insect prey in the diet (Generalized linear mixed model with Poisson and Gamma distribution, respectively). BIC, Bayesian information criterion.

Explained variability	Model	df	>AIC	BIC	LogLik	χ^2	χ^2 df	P
Insect abundance	Null (abundance: +1, locality: random effect)	2	4909.9	4916.3	−2453
	Abundance: species	10	2141.7	2173.4	−1060.9	2784.2	8	<0.001
	Abundance: species + 14‐day period	15	1553.5	1601.1	−761.8	598.2	5	<0.001
	Abundance: species + 14‐day period + habitat	16	1147.8	1198.5	−557.9	407.8	1	<0.001
Proportion of insects in the diet	Null (proportion of insects: +1, locality: random factor)	2	377.0	379.6	−186.5
	Proportion of insects: day in the season	3	252.9	256.8	−123.4	126.1	1	<0.001

Figure 3 Hunting habitat preferences of Little Owls in meadows and fields based on telemetry (n = 307 locations), and the proportional abundance of Pterostichus melanarius (n = 212 individuals) from traps in meadows and fields within Little Owl territories (2 × 2 tables, χ² = 47.5, df = 1, P < 0.0001).