Venturing out of Overwinter Refuge: A Case of Winter Predation on Podarcis tauricus (Georgi, 1801) (Squamata: Lacertidae) by Lanius excubitor Linnaeus, 1758 (Aves: Laniidae) in Greece

Abstract

Shrikes (Lanius spp.) are predatory passerines with a diverse diet that often includes lizards, yet their feeding ecology in Greece remains poorly documented. Here, we report the first case of the great grey shrike Lanius excubitor Linnaeus, 1758 preying on the Balkan wall lizard Podarcis tauricus (Georgi, 1801) in Greece. The observation was made in January 2023 in Central Macedonia under unusually mild winter conditions (~20 °C). The shrike captured and impaled an adult female lizard on a thorn. This record extends the known prey spectrum of the species and underscores the influence of climatic anomalies on predator–prey interactions.

Shrikes belong to the family Laniidae (Aves: Passeriformes), which, according to recent phylogenetic analyses, is monogeneric, with Lanius as the only included genus comprising 32 species [1]. The genus name Lanius, derived from the Latin word for “butcher”, reflects the feeding habits of its members; the most distinctive habit is the use of thorns, palm leaves, barbed wires or other sharp objects to deposit their prey, points known as “larders”, which includes both invertebrates and small vertebrates [2,3,4,5,6,7].

Among the European representatives, the great grey shrike Lanius excubitor Linnaeus, 1758, is resident across central, northern, and eastern Europe, extending eastward to Kazakhstan and western Siberia; during severe winters, however, it migrates short distances southward, occasionally reaching as far as the southernmost Balkans [8,9,10,11]. In Greece, it is considered a fairly widespread yet a rare winter visitor, occurring mainly in the northeastern mainland and only sporadically elsewhere [12]. Despite this wide distribution, the feeding ecology of this medium-sized passerine (measuring 22 to 26 cm) has not been systematically studied in Greece, although studies conducted on other parts of its range show that it has a diverse and seasonally variable diet dominated by arthropods and micromammals, followed by reptiles, amphibians, and birds [9,10,13,14,15,16,17,18,19,20]; within the latter group, lizards frequently constitute the primary prey [10,13,18].

Given the importance of lizards in the diet of shrikes [10,13,18], it is essential to consider the ecology of potential reptilian prey species occurring within their wintering grounds. Lizards (order Squamata) comprise thousands of species across 43 families, with Lacertidae representing the dominant group in Europe and widely distributed throughout the Old World [21,22]. One of the southeastern European representatives of lacertids is the Balkan wall lizard Podarcis tauricus (Georgi, 1801) (Squamata: Lacertidae), whose range extends into mainland Greece, where it occurs east of the Pindos Mountains through Thrace, with the southernmost records in east-central parts of the country [23].

This diurnal, predominantly terrestrial species, with a typical snout–vent length (SVL) of about 80 mm, remains active for much of the year and can occasionally be observed even in winter under favorable weather conditions [24]. To avoid predation, it typically retreats into dense vegetation [25] or ground hollows [26]. High rates of tail breakage and regeneration further indicate strong predation pressure [25,27], while documented predators include amphibians [28], birds [29], and mammals [30].

Despite this evidence of predation, no interaction between the Balkan wall lizard and shrikes has been documented to date. Here, we present the first record of the great grey shrike preying on the Balkan wall lizard, which also constitutes the first confirmed prey record of this shrike species in Greece.

On 18 January 2023 at 14:50 h during a birdwatching excursion around Kerkini Lake-Strymon River in Central Macedonia, Greece (41.2514° N, 23.2412° E, 38  m  a.s.l.), we observed from a distance of about 30 m a great grey shrike, perched on a garland thorn Paliurus spina-christi (Rosales: Rhamnaceae). After a few minutes, when the bird became aware of our presence, it dived towards the ground, on a prey item it had spotted. To our surprise the bird was able to seize a lizard among the grasses at the edge of the pasture (Figure 1A). The lizard was killed within about one minute, after which the shrike took off and impaled its prey on a nearby garland thorn, approximately one meter above the ground (Figure 1B). During the incident photographs were taken to identify the lizard species, but since the great grey shrike stocked the lizard and left, we were able to approach, and inspect it up close (Figure 1C,D) and determine that it was a Balkan wall lizard. The prey-lizard was an adult female with SVL of approximately 75 mm, and an intact tail. This SVL estimate was obtained non-invasively from high-resolution photographs by scaling the lizard’s body length against the diameter of adjacent Paliurus spina-christi thorn and stem structures, which provide consistent and measurable reference points, yielding an estimated precision of approximately ±2–3 mm. Although the observation took place in mid-winter, weather conditions were favorable for lizard activity: sunny with a few clouds, air temperature around 19 °C, and wind intensity approximately 2 Beaufort. The habitat at the site consisted of pastureland used for buffaloes, cattle, and sheep [31], characterized by flattened grass meadows interspersed with sparse garland thorn shrubs and bordering with a river bank.

To our knowledge, this observation represents the first documented case of predation on the Balkan wall lizard by a great grey shrike and, more broadly, the first confirmed prey record of this shrike in Greece. Predation on lizards by members of the genus Lanius is well documented across their distribution, with shrikes exploiting a wide diversity of lizard species [3,4,5,7,32,33,34]. Studies of shrike trophic ecology consistently suggest that lizards preyed upon tend to be common and widespread species in the areas where such studies have been conducted. In the literature, the most frequently reported lizard prey of the great grey shrike is the viviparous lizard Zootoca vivipara (Lichtenstein, 1823) [13,15,18,19,35,36], followed by the sand lizard Lacerta agilis Linnaeus, 1758 [9,10,36] and the slow worm Anguis fragilis Linnaeus, 1758 [36]. Our record extends this prey spectrum by documenting the Balkan wall lizard Podarcis tauricus as an additional species taken by the great grey shrike.

The absence of previous records may reflect both the scarcity of systematic dietary studies in regions where the two species co-occur and the low probability of opportunistic observations. In northern Greece, the Balkan wall lizard is a widespread reptile (pers. obs.; [37,38]), whereas the great grey shrike occurs only as a scarce winter visitor [12]. Beyond their overlapping distributions, shared habitat preferences likely facilitated this interaction: traditional farmland mosaics and open areas with sparse shrubs, such as low vegetation grasslands, meadows, forest clearings, woodland edges, and roadsides, provide both suitable microhabitats for Balkan wall lizards [24,25,26,37,39] and preferred foraging grounds for great grey shrikes [8,40,41]. In addition, the unusually mild weather conditions during the week of observation, with daytime temperatures reaching approximately 20 °C, likely favored winter lizard activity and thus increased the probability of predation. Meteorological data from the nearest Hellenic National Meteorological Service station at Kerkini support this interpretation, with a maximum of 20.5 °C recorded on 18 January compared to a long-term regional January mean of 8.1 °C [42]. This warm spell occurred within a broader regional trend of winter warming: Kerkini is among the Greek inland waterbodies exhibiting a significant multi-decadal increase in winter thermal conditions, with recurrent mid-winter warm excursions documented over the past 40 years [43]. While this does not establish causality, such pronounced warm spells can temporarily relax thermal constraints on lacertid activity, enabling occasional winter surface movements and increasing the likelihood of opportunistic encounters with predators. Such events highlight how short-term climatic anomalies may generate unexpected ecological interactions that would otherwise remain undetected, emphasizing the importance of incidental records in documenting predator–prey dynamics. Future studies should therefore investigate the intensity of predation on the Balkan wall lizard by the great grey shrike and other congeneric species, in order to clarify their role in local food webs and to assess how interannual variation in winter temperature regimes may influence such interactions in regions of sympatry.