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.
- Other Geographic Terms
- holarctic
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.
- Habitat Regions
- temperate
- terrestrial
- Terrestrial Biomes
- tundra
- taiga
- desert or dune
- savanna or grassland
- forest
- Other Habitat Features
- agricultural
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.
- Other Physical Features
- endothermic
- bilateral symmetry
- Sexual Dimorphism
- sexes alike
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.
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.
- Mating System
- monogamous
- polygynandrous (promiscuous)
- cooperative breeder
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.
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.
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- oviparous
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.
- Parental Investment
- altricial
- male parental care
- female parental care
-
pre-hatching/birth
-
protecting
- female
-
protecting
-
pre-weaning/fledging
-
provisioning
- male
- female
- protecting
-
provisioning
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.
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.
- Key Behaviors
- arboreal
- flies
- diurnal
- crepuscular
- motile
- nomadic
- migratory
- sedentary
- territorial
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.
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.
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.
- Primary Diet
-
carnivore
- eats terrestrial vertebrates
- insectivore
- Animal Foods
- birds
- mammals
- amphibians
- reptiles
- insects
- terrestrial non-insect arthropods
- Foraging Behavior
- stores or caches food
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.
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.
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.
Additional Links
Contributors
Theresa McHugh (author), Indiana University-Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne, Leila Siciliano Martina (editor), Texas State University.
- 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.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Palearctic
-
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Ethiopian
-
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- holarctic
-
a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.
Found in northern North America and northern Europe or Asia.
- 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.
- 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.
- 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.
- 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.
- 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.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- agricultural
-
living in landscapes dominated by human agriculture.
- monogamous
-
Having one mate at a time.
- polygynandrous
-
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
- cooperative breeder
-
helpers provide assistance in raising young that are not their own
- 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).
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- oviparous
-
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- 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.
- male parental care
-
parental care is carried out by males
- female parental care
-
parental care is carried out by females
- arboreal
-
Referring to an animal that lives in trees; tree-climbing.
- diurnal
-
- active during the day, 2. lasting for one day.
- crepuscular
-
active at dawn and dusk
- motile
-
having the capacity to move from one place to another.
- nomadic
-
generally wanders from place to place, usually within a well-defined range.
- migratory
-
makes seasonal movements between breeding and wintering grounds
- sedentary
-
remains in the same area
- 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
- visual
-
uses sight to communicate
- acoustic
-
uses sound to communicate
- mimicry
-
imitates a communication signal or appearance of another kind of organism
- 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
- choruses
-
to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- stores or caches food
-
places a food item in a special place to be eaten later. Also called "hoarding"
- carnivore
-
an animal that mainly eats meat
- insectivore
-
An animal that eats mainly insects or spiders.
- 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.
- 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.
References
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