Lanius excubitorgreat grey shrike(Also: great grey shrike;northern shrike; northern shrike)

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Geographic Range

Great grey shrikes (Lanius excubitor), also known as northern shrikes or northern grey shrikes, have a Holarctic distribution and are found in North America, Europe, Asia and Africa. Their breeding range includes the northern United States, Canada, Norway, Spain, France, Poland, Sweden, Russia and China as well as other Eurasian countries. Wintering sites are found in southern locations of the same countries and the northern continental United States. (Atkinson and Cade, 1993; Brady, et al., 2009; Cramp and Perrins, 1993; Hernandez, 1995; Peer, et al., 2011)

Habitat

Great grey shrikes are often found in semi-open areas composed of farmlands, field hedges, arable fields, meadows and pastures as well as coniferous and mixed forests. Shrikes prefer lowlands and tend to avoid higher elevations. (Antczak, Marcin, 2010; Degen, et al., 1992; Kuczynski, et al., 2010; Olborska and Kosicki, 2004; Tryjanowski, et al., 2007)

  • Range elevation
    1400 (high) m
    4593.18 (high) ft

Physical Description

Great grey shrikes are medium-sized passerines, about the size of large thrushes or mockingbirds. They range in length from 22 to 26 cm, with a wingspan of 30 to 36 cm. They weigh between 48 and 80 g, however, most range between 60 and 70 g. Their upper parts are pearl grey. Their cheeks, chin and the stripe above their eyes are white. A dark mask extends from their beak past their eyes to their ear coverts. The space immediately above their beak is grey. Their shoulder feathers are white and their wings are black with white tufts. Their tail is black and pointed at the tip; the most distal edges of their tail are white. Their ventral parts tend to be white or tinged grey. Their breast is often slightly darker than the rest of their underside. Their legs and feet are black. Males and females are about the same size and coloration, females tend to be tinged in brown, but have the same overall color patterns. Fledglings resemble females, as they are greyish-brown all over. They have barring and pastel yellow markings on their upper parts. Their wing coverts are pastel yellow and have black bands. Young shrikes acquire their adult plumage during their first spring. (Brady, et al., 2009; Brzezinski, et al., 2010; Harris and Franklin, 2000)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    48 to 81 g
    1.69 to 2.85 oz
  • Average mass
    60-70 g
    oz
  • Range length
    22 to 26 cm
    8.66 to 10.24 in
  • Range wingspan
    30 to 36 cm
    11.81 to 14.17 in

Reproduction

Great grey shrikes are territorial, socially monogamous birds; however, extra-pair copulations (EPCs) are frequent in both males and females, making them semi-polygynandrous. As opposed to within pair copulations (WPCs), which occur in open places such as near electrical lines, fences or the tops of trees, EPCs occur in more secretive locations. During pre-copulatory displays, a male faces a female, shivering and fluttering his wings while calling or quietly singing. Males often offer a food item as a nuptial gift. Pre-copulatory gifts before EPCs have an energetic value of about four-fold of those given before WPCs. If a male detects an EPC, he often attempts mating with his partner shortly thereafter; however, females seem to control copulation. Copulations are most frequent in the early morning. (Antczak, et al., 2005; Antczak, et al., 2012; Lorek, 1995; Tryjanowski, et al., 2007)

Courtship begins around March and lasts until April or May. Males participate in courtship displays and maintain caches to attract females. Impaling prey may be a sexual display for males as they impale prey in conspicuous places significantly more often than females. The size of their cache is indicative of the male's health. By storing caches in more conspicuous places and returning frequently to those caches, males can display their hunting prowess and entice a female. Males may also sit at a right angle to the desired female as part of the display. Males also attract females through song. Sounds associated with calls to females include a mix of whistles and strophes of songs. Softer whistles may be used in duets between mates during wintering and between neighbors during breeding seasons. Song phrases interspersed with harsh whistles are often used in pre-courtship, songs become softer as males introduce females to their territory, with lively chatters indicating potential nesting sites. A female usually rejects males at first, only allowing them to feed her, but eventually females participate in the displays and their songs become duets. Copulation usually begins after a male brings a prey item to his mate and performs a pre-copulatory display. Male and female shrikes produce a begging call until they are adjacent to one another. The male bobs his body left and right and gives prey to the female, followed by copulation. Once nesting begins, breeding groups disperse. A male feeds his mate and closely guards her, perching high up to watch for threats. During this time, males often stray into one another's territory to obtain a quick EPC; as a result, their nests often contain offspring from multiple males. Clutches are usually produced within 10 to 15 days. Cooperative breeding sometimes occurs. Other adults also occasionally assist in feeding offspring; these "helpers" may be offspring from the previous year. (Antczak, et al., 2005; Antczak, et al., 2012; Lorek, 1995; Tryjanowski, et al., 2007)

Great grey shrikes like to breed in dispersed groups of six or more individuals. They breed during the summer, generally once, but sometimes twice in a year. During the breeding season, the monogamous pair bond is particularly strong, but during the wintering season, it loosens and a new mate may be chosen. Pairs produce one brood each year but replacement clutches can occur after nest failures. Nesting usually begins in April or May; pairs construct nests in about one to two weeks. Nests from previous years are often reused with minor alterations. Nests are usually located at least 1 m above ground, but usually range from 2 to 16 m above ground. The pair builds nests together, but males collect the majority of the nest materials. Nests tend to be quite large, 20 to 28 cm in outer diameter, made of twigs, moss, pieces of fabric and sometimes pieces of trash. The inner diameter of the nest is about 8 to 12 cm and 10 to 15 cm deep, lined with twigs, roots, lichens, hairs and feathers. Breeding and nesting territory is highly flexible, but most nests are located centrally in the territory, with convenient perches for monitoring the territory. Nests are often located in a tree or thorny bush and range in height from 0.2 to 25.0 meters. (Harris and Franklin, 2000; Hernandez, 1995; Olborska and Kosicki, 2004; Tryjanowski, et al., 2007)

Laying usually occurs in May with 3 to 9 eggs per clutch and an average of 7 eggs total. Second clutches, if produced, are smaller than the first. Eggs are grey or blue and have yellow, red-brown and purple-grey blotches; they are about 26 mm long and 19.5 mm wide. The 16 to 21 day incubation period is completed by the female, while the male provides her with food. Hatchlings are naked, blind and pink-skinned, weighing about 4 g. Offspring fledge after 2 to 3 weeks, usually in June or July, and become independent 3 to 6 weeks later. Offspring become sexually mature during their first spring and attempt to breed immediately. Great grey shrikes attempt breeding about four times in their life. (Harris and Franklin, 2000; Hernandez, 1995; Olborska and Kosicki, 2004; Tryjanowski, et al., 2007)

  • Breeding interval
    Great grey shrikes breed in the summer months, once yearly and in rare cases, twice in a year.
  • Breeding season
    Breeding occurs between April and May; nests are built during both months, laying taking place in May.
  • Range eggs per season
    3 to 9
  • Average eggs per season
    7
  • Range time to hatching
    21 (high) days
  • Average time to hatching
    16 days
  • Range fledging age
    2 to 3 weeks
  • Range time to independence
    3 to 6 weeks
  • Range age at sexual or reproductive maturity (female)
    1 (low) years
  • Range age at sexual or reproductive maturity (male)
    1 (low) years

During the pre-hatching stage, males provide food for their mates, this way females can dedicate all of their time to incubating the eggs. After the eggs hatch, females brood the offspring, as they age, females assist males in food provisioning. Weak fledglings receive extra care and feeding from either, or both parents. (Harris and Franklin, 2000)

Lifespan/Longevity

The lifespan of great grey shrikes is usually about four years. The oldest known individual lived twelve years. Predatory birds and carnivorous mammals often kill shrikes before they reach a fifth year. Their greatest threat is raptorial birds during their fledgling period. (Harris and Franklin, 2000)

  • Range lifespan
    Status: wild
    12 (high) years
  • Average lifespan
    Status: wild
    4 years
  • Average lifespan
    Status: wild
    4 years

Behavior

Great grey shrikes are diurnal birds that travel frequently through a range about three times the size of their territory and have seasonal migrations to breeding and wintering grounds. They are territorial, but tend to live in groups of about six or more pairs and become more solitary during the breeding season. These birds actively try to prevent EPCs of their mates. Outside of breeding season, groups of breeding birds will gather together and interact through flight displays, chattering and calling to one another for up to an hour. Great grey shrikes fly in a heavy, undulating pattern, but when attacking, fly in a straight, determined direction. These birds can also hover for a brief amount of time. When encountering a conspecific, they show aggression by shifting to a horizontal position and fluffing their feathers, forming crests along their head. To show submission to a conspecific, they may turn their head away or display a crouching, fluttering position while imitating a fledgling call. To prevent attack by a conspecific, the birds point their beak vertically upward. (Antczak, et al., 2005; Harris and Franklin, 2000)

  • Range territory size
    0.2 to 3.5 km^2
  • Average territory size
    0.4 km^2

Home Range

Great grey shrikes have a relatively flexible preference in breeding territory and nesting sites. They have a large home range of 20,000 km^2 and groups tend to be about 5 km away from one another. They can have territories as small as 20 ha, but 40 ha are more common, territories as large as 350 ha have also been reported. (Antczak, Marcin, 2010; Atkinson, 1997; Harris and Franklin, 2000; Olborska and Kosicki, 2004)

Communication and Perception

Great grey shrikes use vocalizations, body positions and food caches to communicate. Both male and female shrikes sing year round and use a variety of calls including alarm calls, courtship calls, submission calls, prey-attracting calls and nestling calls. Warning songs may consist of warbling strophes and whistles to indicate a small-sized intruder. For larger intruders, they may produce a long shrill, with raspy whistles. Warnings against birds of prey often have a sharp whistle. A harsh call is often repeated twice when the bird is alarmed, calls become faster and higher the more excited the bird becomes. When their young are threatened, they emit a "knuk" sound. Softer whistles are often used by males communicating with females and in duets between mates. To show submission to a conspecific, great grey shrikes may imitate the fledgling "waik" call. In attracting songbird prey, these birds also mimic calls, which may quite successful. When great grey shrikes encounter predators, or when preparing to attack prey, they perform aggressive body movements including bobbing and twisting, oriented on the horizontal plain, while flipping their tail rapidly up and down. Quivering, fluttering and flashing movements are often responses to hunting preparation as well as reactions toward predators. Wing communication is also used during courtship-feeding. Males often quiver and flutter their wings before presenting females with food. In soliciting food from males, females quiver and flutter their wings in return. Great grey shrikes may also use UV light and scent to detect vole locations and abundance. (Antczak, et al., 2012; Atkinson, 1997; Cade, 1962; Harris and Franklin, 2000; Probst, et al., 2002)

Food Habits

Great grey shrikes are carnivorous generalists. They search for prey by actively scanning the surrounding area and perching in an upright and alert posture, changing perches frequently. They are very successful hunters as they usually surprise their prey. Once a prey item has been located, great grey shrikes drop-pounce from their elevated perch, hover and chase small passerines. Shrikes kill by using their hooked beak to crack the skull of their prey. Once the prey is captured, great grey shrikes impale large prey items upon stumps, thorns or barbed-wire. After impalement, prey items become easier to tear apart and consume. Great grey shrikes cache prey items, primarily during the non-breeding period to indicate claimed territory, attract females and hide it from competitors. Prey is often cached in thorny bushes such as hawthorns and blackthorns. They usually consume all of their prey within nine days. Their dietary preferences depend on where they live and the food sources available. In southern Europe, they feed primarily on orthopterans and beetles, whereas in northern and central Europe, mammals and birds are a larger portion of their diet. Invertebrates, as well as vertebrates, compose their diet. Arthropods are their most frequent prey item, namely beetles including ground beetles, dung beetles, rove beetles and darkling beetles. Other insects in their diet include bumblebees. Small mammals are also a large portion of their diet including common voles, field voles, deer mice, harvest mice and wild house mice. Their avian prey includes dark-eyed juncos, white-crowned sparrows, black-capped chickadees, pine siskins, European starlings, house sparrows and members of the genera Carduelis and Carpodacus. Shrikes may attract small passerine birds within attack range by imitating parts of their calls and songs. Lizards and frogs are caught on occasion, but are frequently left in caches and not eaten. (Atkinson and Cade, 1993; Atkinson, 1997; Brzezinski, et al., 2010; Hernandez, 1995)

  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles
  • insects
  • terrestrial non-insect arthropods

Predation

Predators of great grey shrikes include mammals and other birds. Members of family Corvidae have been known to prey upon their eggs and nestlings. Raptorial birds also present a threat to shrikes, but this occurs primarily after fledging. Likewise, little owls are known predators of great grey shrikes. When predators approach, great grey shrikes often vocalize and ruffle their feathers. Various types of warning calls are made depending on the size and proximity of the predator. (Cade, 1962; Harris and Franklin, 2000)

Ecosystem Roles

In the past, nests of great grey shrikes were invaded by eggs from common cuckoos; however, these brood parasites are likely now extinct. Parasite-host coevolution seems to have occurred, the high levels of parasite egg rejection suggests parasite defense mechanisms are rooted in this bird's evolutionary history. There has been one recorded case of interspecific helping, where yellowhammers were found feeding a great grey shrike fledgling, although great grey shrikes are larger. Some birds, including whinchats and skylarks, have been observed intentionally avoiding a particular breeding ground due to presence of great grey shrikes, a known predator. Since great grey shrikes are one of the first birds to occupy their territory in the spring, this may influence the breeding bird assemblage near their nests. Their body size may influence their primary prey choice, smaller birds forage mainly on beetles, whereas larger birds more frequently prey on flying and plant-dwelling insects. (Drozdz, et al., 2004; Harris and Franklin, 2000; Hromada, et al., 2003; Hromada, et al., 2002; Peer, et al., 2011)

Economic Importance for Humans: Positive

There are no known benefits of great grey shrikes to humans.

Economic Importance for Humans: Negative

There are no known adverse effects of great grey shrikes on humans.

Conservation Status

Great grey shrikes have an extensive range in the Holarctic region and are listed as an IUCN Red List species of Least Concern. They have become extinct in Switzerland and the Czech Republic, but the extent of their geographic range is large enough that overall populations have remained stable. They are sensitive to landscape changes and reductions in hedgerows and other shrubs. There are often hundreds to thousands of great grey shrikes within each country they inhabit, with particularly large populations in Sweden. Countries with smaller populations include Estonia, Belgium, Latvia, Lithuania, Netherlands and Denmark, with only a few hundred birds or less found in each country. (Harris and Franklin, 2000)

Contributors

Theresa McHugh (author), Indiana University-Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne, Leila Siciliano Martina (editor), Animal Diversity Web Staff.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

choruses

to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species

cooperative breeder

helpers provide assistance in raising young that are not their own

crepuscular

active at dawn and dusk

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

diurnal
  1. active during the day, 2. lasting for one day.
duets

to jointly display, usually with sounds in a highly coordinated fashion, at the same time as one other individual of the same species, often a mate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

holarctic

a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.

World Map

Found in northern North America and northern Europe or Asia.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

migratory

makes seasonal movements between breeding and wintering grounds

mimicry

imitates a communication signal or appearance of another kind of organism

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nomadic

generally wanders from place to place, usually within a well-defined range.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

taiga

Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

tundra

A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.

visual

uses sight to communicate

References

BirdGuides. 2013. "Great Grey Shrike (Lanius excubitor)" (On-line). BirdGuides. Accessed March 07, 2013 at http://www.birdguides.com/species/species.asp?sp=122072.

Cornell Lab of Ornithology. 2010. "Northern Shrike" (On-line). All About Birds. Accessed March 07, 2013 at http://www.allaboutbirds.org/guide/Northern_Shrike/id.

Antczak, Marcin, 2010. Winter nocturnal roost selection by a solitary passerine bird, the Great Grey Shrike Lanius excubitor. Ornis Fennica, 87: 99-105.

Antczak, M., M. Hromada, P. Tryjanowski. 2005. Frogs and toads in the food of the Great Grey Shrike (Lanius excubitor): larders and skinning as two ways to consume dangerous prey. Animal Biology, 55 (3): 227-233.

Antczak, M., M. Hromada, P. Tryjanowski. 2012. Sex differences in impaling behavior of Great Grey Shrike Lanius excubitor: Do males have better impaling skills than females. Behavioural Processes, 91: 50-53.

Atkinson, E. 1997. Singing for your supper: acoustical luring of avian prey by Northern Shrikes. The Condor, 99 (1): 203-206.

Atkinson, E., T. Cade. 1993. Winter foraging and diet composition of Northern Shrikes in Idaho. The Condor, 95 (3): 528-535.

Birdlife International, 2012. "Lanius excubitor" (On-line). IUCN Red List of Threatened Species. Accessed March 07, 2013 at http://www.iucnredlist.org/details/160031195/0.

Brady, R., J. Paruk, A. Kern. 2009. Sexing adult Northern Shrikes using DNA, morphometrics, and plumage. Journal of Field Ornithology, 80 (2): 198-205.

Brzezinski, M., A. Zalewski, P. Szalanski, R. Kowalczyk. 2010. Feeding habits of the Great Grey Shrike Lanius excubitor wintering in north-eastern Poland: does prey abundance affect selection of prey size. Ornis Fennica, 87: 1-14.

Cade, T. 1962. Wing movements, hunting, and displays of the Northern Shrike. Wilson Bulletin, 74: 386-408.

Cramp, S., C. Perrins. 1993. Handbook of birds of Europe, the Middle East and North Africa. Oxford: Oxford University Press.

Degen, A., B. Pinshow, R. Yosef, M. Kam, K. Nagy. 1992. Energetics and growth rate of Northern Shrike (Lanius excubitor) nestlings. Ecology, 73 (6): 2273-2283.

Drozdz, R., M. Hromada, P. Tryjanowski. 2004. Interspecific feeding of a Great Grey Shrike (Lanius excubitor) fledgling by adult Yellowhammers (Emberiza citrinella). Biological Letters, 41(2): 185-187.

Harris, T., K. Franklin. 2000. Shrikes & bush-shrikes: including wood-shrikes, helmet-shrikes, flycatcher-shrikes, philentomas, batises and wattle-eyes. London: Christopher Helm.

Hernandez, A. 1995. Spatial patterns of food caching in two sympatric shrike species. The Condor, 97 (4): 1002-1010.

Hromada, M., M. Antczak, T. Valone, P. Tryjanowski. 2008. Settling decisions and heterospecific social information use in shrikes. PLoS ONE, 3(12): e3930.

Hromada, M., L. Kuczynski, A. Kristin, P. Tryjanowski. 2003. Animals of different phenotype differentially utilize dietary niche—the case of the Great Grey Shrike Lanius excubitor. Ornis Fennica, 80: 1-8.

Hromada, M., P. Tryjanowski, M. Antczak. 2002. Presence of the great grey shrike Lanius excubitor affects breeding passerine assemblage. Annales Zoologici Fennici, 39: 125-130.

Kuczynski, L., M. Antczak, P. Czechowski, J. Grzybek, L. Jerzak, P. Zablocki, P. Tryjanowski. 2010. A large scale survey of the Great grey shrike Lanius excubitor in Poland: breeding densities, habitat use and population trends. Annales Zoologici Fennici, 47: 67-78.

Lorek, G. 1995. Copulation behavior, mixed reproductive strategy, and mate guarding in the Great Grey Shrike. Proceedings of the Western Foundation of Vertebrate Zoology, 6: 218-227.

Olborska, P., J. Kosicki. 2004. Breeding biology of the Great Grey Shrike (Lanius excubitor): an analysis of nest record cards. Biological Letters, 41 (2): 147-154.

Peer, B., C. McIntosh, M. Kuehn, S. Rothstein, R. Fleischer. 2011. Complex biogeographic history of Lanius shrikes and its implications for the evolution of defenses against avian brood parasitism. The Condor, 133 (2): 385-394.

Probst, R., M. Pavlicev, J. Viitala. 2002. UV reflecting vole scent marks attract a passerine, the great grey shrike Lanius excubitor. Journal of Avian Biology, 33: 437-440.

Tryjanowski, P., M. Antezak, M. Hromada. 2007. More secluded places for extra-pair copulations in the Great Grey Shrike Lanius excubitor. Behaviour, 144 (1): 23-31.

Yosef, R. 1992. From nestbuilding to fledging of young in Great Grey Shrikes (Lanius excubitor) at Sede Boqer, Israel. Journal fur Ornithologie, 133 (3): 279-285.