Mexican Jay
Encyclopedia
The Mexican Jay, Aphelocoma wollweberi, formerly known as the Gray-breasted Jay, is a New World
jay native to the Sierra Madre Oriental
, Sierra Madre Occidental
, and Central Plateau
of Mexico
. It reaches north to eastern Arizona
, western New Mexico
and western Texas
in the United States
. Its preferred habitat is montane pine
-oak
forest.
Note, in May 2011, the American Ornithologists' Union voted to split the Mexican Jay into two species, one retaining the common name Mexican Jay and one called the Transvolcanic Jay
(see below).
The Mexican Jay is a medium-large (~120 g) passerine similar in size to most other jay
s, with a blue head, blue-gray mantle, blue wings and tail, and pale gray breast and underparts. The sexes are morphologically similar, and juveniles differ only in having less blue coloration and, in some populations, a pink/pale (instead of black) bill that progressively becomes more black with age (Brown and Horvath 1989). Some field guides misreport this color as yellow because the pale bill becomes yellow in museum study skins. The iris is brown and legs are black. It is most readily distinguished from the similar Western Scrub-Jay by the plain (unstreaked) throat and breast, and the mantle contrasting less with the head and wings. Its range somewhat overlaps with the Western Scrub-Jays, but, where they co-occur, the two species seem to show ecological and morphological character displacement
(Curry et al. 2002).
In the winter, the Mexican Jay's diet consists mainly of acorn
s and pine nut
s, which are stored in the autumn. However, they are omnivorous in all seasons and their diet includes a wide variety of plant and animal matter, including invertebrates, small amphibians and reptiles, and birds' eggs and nestlings (McCormack and Brown 2008).
It has a cooperative breeding
system similar to that of the related Florida Scrub-Jay, with several birds helping at a nest; these 'helpers
' are usually immature offspring of the dominant pair from the previous 1–2 years, but also include apparently unrelated flock members.
Thus, as of this decision, there are now five described subspecies of Mexican Jays that are divided into three divergent groups (see below). Marked differences in size, color, vocalizations, and genetics have led some authors to consider at least two of these groups as separate species (East and West; Navarro-Sigüenza and Peterson 2004). The three groups inhabit three distinct mountainous regions in northern and central Mexico. Genetic breaks in mitochondrial and microsatellite DNA occur abruptly between the groups, indicating some barriers to genetic exchange (McCormack et al. 2008). Size variation among the groups does not always follow Bergman's Rule, with more southerly populations in the Sierra Madre Oriental being larger than populations to the north. Mexican Jays do not seem to follow Gloger's Rule
either as populations in arid habitat in southwestern Texas are very blue. On the other hand, Mexican jays in Arizona - also arid habitat - have a washed-out appearance, in accordance with Gloger's Rule
.
Western group
Sierra Madre Occidental
in northern [Jalisco] north to central Arizona
and southwestern New Mexico
. Southern and eastern limits in Jalisco deserve further study. Juveniles have a pink/pale base to the otherwise black bill for up to two years. Eggs are pale green-blue and unspeckled, unlike Eastern group where speckled eggs are common.
Eastern group
Sierra Madre Oriental
in Nuevo León
and W Tamaulipas
north to Texas
(Chisos Mountains
). Juveniles have an all-black exterior to the bill after fledging, but roof of inner upper mandible can remain partially white for up to two years. Reports of less social behavior compared to other groups are over-stated and credible accounts of cooperative breeding (Ligon and Husar 1974) and large flock sizes
(Bhagabati and Horvath 2006) exist. Plain, speckled, and even white eggs have been observed in a single study area (McCormack and Berg 2010).
Central Plateau group
Central Plateau
in Queretaro
, Guanajuato
, San Luis Potosi
, and eastern Jalisco
. Similar to Eastern group but larger in most features. Distinguishable in morphology and plumage in ~80% of specimens. There is an area of apparent hybridization in San Luis Potosi that deserves study.
New World
The New World is one of the names used for the Western Hemisphere, specifically America and sometimes Oceania . The term originated in the late 15th century, when America had been recently discovered by European explorers, expanding the geographical horizon of the people of the European middle...
jay native to the Sierra Madre Oriental
Sierra Madre Oriental
The Sierra Madre Oriental is a mountain range in northeastern Mexico.-Setting:Spanning the Sierra Madre Oriental runs from Coahuila south through Nuevo León, southwest Tamaulipas, San Luis Potosí, Querétaro, and Hidalgo to northern Puebla, where it joins with the east-west running Eje Volcánico...
, Sierra Madre Occidental
Sierra Madre Occidental
The Sierra Madre Occidental is a mountain range in western Mexico.-Setting:The range runs north to south, from just south of the Sonora–Arizona border southeast through eastern Sonora, western Chihuahua, Sinaloa, Durango, Zacatecas, Nayarit, Jalisco, Aguascalientes to Guanajuato, where it joins...
, and Central Plateau
Central Plateau
Central Plateau is the name of several plateaux.*Central Plateau, New Zealand*Central Siberian Plateau*Central Plateau *Swiss Plateau...
of Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. It reaches north to eastern Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
, western New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
and western Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. Its preferred habitat is montane pine
Pine
Pines are trees in the genus Pinus ,in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.-Etymology:...
-oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...
forest.
Note, in May 2011, the American Ornithologists' Union voted to split the Mexican Jay into two species, one retaining the common name Mexican Jay and one called the Transvolcanic Jay
Transvolcanic Jay
The Transvolcanic Jay is a medium-large passerine similar in size to most other jays, with a blue head, blue-gray mantle, blue wings and tail, gray breast and underparts. The sexes are morphologically similar, and juveniles differ only in having less blue coloration. The iris is brown and legs...
(see below).
The Mexican Jay is a medium-large (~120 g) passerine similar in size to most other jay
Jay
The jays are several species of medium-sized, usually colorful and noisy, passerine birds in the crow family Corvidae. The names jay and magpie are somewhat interchangeable, and the evolutionary relationships are rather complex...
s, with a blue head, blue-gray mantle, blue wings and tail, and pale gray breast and underparts. The sexes are morphologically similar, and juveniles differ only in having less blue coloration and, in some populations, a pink/pale (instead of black) bill that progressively becomes more black with age (Brown and Horvath 1989). Some field guides misreport this color as yellow because the pale bill becomes yellow in museum study skins. The iris is brown and legs are black. It is most readily distinguished from the similar Western Scrub-Jay by the plain (unstreaked) throat and breast, and the mantle contrasting less with the head and wings. Its range somewhat overlaps with the Western Scrub-Jays, but, where they co-occur, the two species seem to show ecological and morphological character displacement
Character displacement
Character displacement refers to the phenomenon where differences among similar species whose distributions overlap geographically are accentuated in regions where the species co-occur but are minimized or lost where the species’ distributions do not overlap. This pattern results from evolutionary...
(Curry et al. 2002).
In the winter, the Mexican Jay's diet consists mainly of acorn
Acorn
The acorn, or oak nut, is the nut of the oaks and their close relatives . It usually contains a single seed , enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad...
s and pine nut
Pine nut
Pine nuts are the edible seeds of pines . About 20 species of pine produce seeds large enough to be worth harvesting; in other pines the seeds are also edible, but are too small to be of great value as a human food....
s, which are stored in the autumn. However, they are omnivorous in all seasons and their diet includes a wide variety of plant and animal matter, including invertebrates, small amphibians and reptiles, and birds' eggs and nestlings (McCormack and Brown 2008).
It has a cooperative breeding
Cooperative breeding
Cooperative breeding is a social system in which individuals contribute care to offspring that are not their own at the expense of their own reproduction . When reproduction is monopolized by one or few of the adult group members and most adults do not reproduce, but help rear the breeder’s...
system similar to that of the related Florida Scrub-Jay, with several birds helping at a nest; these 'helpers
Helpers at the nest
Helpers at the nest is a term used in behavioural ecology and evolutionary biology to describe a social structure in which juveniles and sexually mature adolescents of either one or both sexes, remain in association with their parents and help them raise subsequent broods or litters, instead of...
' are usually immature offspring of the dominant pair from the previous 1–2 years, but also include apparently unrelated flock members.
Systematics
A recent decision by the American Ornithologists' Union Check-list Committee elevated some populations of the Mexican Jay to a separate species, called the Transvolcanic Jay (A. ultramarina), based on diagnosable phenotypic differences in plumage and morphology, millions of years of genetic divergence, and no evidence for interbreeding with Mexican Jays. The Transvolcanic Jay inhabits montane forest in the Transvolcanic Belt of central Mexico. Populations to the north retained the common name Mexican Jay, but the Latin name changed to A. wollweberi. This was because the type specimen was a Transvolcanic Jay, meaning that this species had precedent for the original Latin name A. ultramarina.Thus, as of this decision, there are now five described subspecies of Mexican Jays that are divided into three divergent groups (see below). Marked differences in size, color, vocalizations, and genetics have led some authors to consider at least two of these groups as separate species (East and West; Navarro-Sigüenza and Peterson 2004). The three groups inhabit three distinct mountainous regions in northern and central Mexico. Genetic breaks in mitochondrial and microsatellite DNA occur abruptly between the groups, indicating some barriers to genetic exchange (McCormack et al. 2008). Size variation among the groups does not always follow Bergman's Rule, with more southerly populations in the Sierra Madre Oriental being larger than populations to the north. Mexican Jays do not seem to follow Gloger's Rule
Gloger's rule
Gloger's Rule is a zoological rule which states that within a species of endotherms, more heavily pigmented forms tend to be found in more humid environments, e.g. near the equator. It was named after the zoologist Constantin Wilhelm Lambert Gloger, who first remarked upon this phenomenon in 1833...
either as populations in arid habitat in southwestern Texas are very blue. On the other hand, Mexican jays in Arizona - also arid habitat - have a washed-out appearance, in accordance with Gloger's Rule
Gloger's rule
Gloger's Rule is a zoological rule which states that within a species of endotherms, more heavily pigmented forms tend to be found in more humid environments, e.g. near the equator. It was named after the zoologist Constantin Wilhelm Lambert Gloger, who first remarked upon this phenomenon in 1833...
.
Western group
Sierra Madre Occidental
Sierra Madre Occidental
The Sierra Madre Occidental is a mountain range in western Mexico.-Setting:The range runs north to south, from just south of the Sonora–Arizona border southeast through eastern Sonora, western Chihuahua, Sinaloa, Durango, Zacatecas, Nayarit, Jalisco, Aguascalientes to Guanajuato, where it joins...
in northern [Jalisco] north to central Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
and southwestern New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
. Southern and eastern limits in Jalisco deserve further study. Juveniles have a pink/pale base to the otherwise black bill for up to two years. Eggs are pale green-blue and unspeckled, unlike Eastern group where speckled eggs are common.
- Aphelocoma wollweberi gracilis
- E NayaritNayaritNayarit officially Estado Libre y Soberano de Nayarit is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 20 municipalities and its capital city is Tepic.It is located in Western Mexico...
and N Jalisco - Smallest of the Western subspecies with a distinct, high-pitched vocalization* Aphelocoma wollweberi wollweberi
- Durango and Zacatecas
- Intermediate in size
- Aphelocoma wollweberi arizonae
- Sonora and Chihuahua north to ArizonaArizonaArizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
and New MexicoNew MexicoNew Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
, USA - Large and most pale of all subspecies.
Eastern group
Sierra Madre Oriental
Sierra Madre Oriental
The Sierra Madre Oriental is a mountain range in northeastern Mexico.-Setting:Spanning the Sierra Madre Oriental runs from Coahuila south through Nuevo León, southwest Tamaulipas, San Luis Potosí, Querétaro, and Hidalgo to northern Puebla, where it joins with the east-west running Eje Volcánico...
in Nuevo León
Nuevo León
Nuevo León It is located in Northeastern Mexico. It is bordered by the states of Tamaulipas to the north and east, San Luis Potosí to the south, and Coahuila to the west. To the north, Nuevo León has a 15 kilometer stretch of the U.S.-Mexico border adjacent to the U.S...
and W Tamaulipas
Tamaulipas
Tamaulipas officially Estado Libre y Soberano de Tamaulipas is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 43 municipalities and its capital city is Ciudad Victoria. The capital city was named after Guadalupe Victoria, the...
north to Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
(Chisos Mountains
Chisos Mountains
The Chisos Mountains are a mountain range located in the Big Bend area of West Texas, USA. The mountain range is contained entirely within the boundaries of Big Bend National Park. This is the only mountain range in the United States to be fully contained within the boundary of a National Park...
). Juveniles have an all-black exterior to the bill after fledging, but roof of inner upper mandible can remain partially white for up to two years. Reports of less social behavior compared to other groups are over-stated and credible accounts of cooperative breeding (Ligon and Husar 1974) and large flock sizes
Group size measures
Many animals, including humans, tend to live in groups, herds, flocks, bands, packs, shoals, or colonies of conspecific individuals. The size of these groups, as expressed by the number of participant individuals, is an important aspect of their social environment...
(Bhagabati and Horvath 2006) exist. Plain, speckled, and even white eggs have been observed in a single study area (McCormack and Berg 2010).
- Aphelocoma wollweberi couchii
- Smaller than preceding. Population of latter species distinguishable by more contrasting markings and ecological preferences (lowland birds). Egg color may range from plain blue to nile blueNile blueNile blue is a stain used in biology and histology. It may be used with live or fixed cells, and imparts a blue colour to cell nuclei....
with pale brownish speckling, most heavy on blunt half. Gives rattle call similar to CyanocittaCyanocittaThe genus Cyanocitta is a New World genus of jays, passerine birds of the family Corvidae. Cyanocitta includes only two of the New World jays; they are blue, crested birds that differ in the colour of the head. Their ranges generally do not overlap....
and Western Scrub-Jays.
Central Plateau group
Central Plateau
Central Plateau
Central Plateau is the name of several plateaux.*Central Plateau, New Zealand*Central Siberian Plateau*Central Plateau *Swiss Plateau...
in Queretaro
Querétaro
Querétaro officially Estado Libre y Soberano de Querétaro de Arteaga is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided into 18 municipalities and its capital city is Santiago de Querétaro....
, Guanajuato
Guanajuato
Guanajuato officially Estado Libre y Soberano de Guanajuato is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 46 municipalities and its capital city is Guanajuato....
, San Luis Potosi
San Luis Potosí
San Luis Potosí officially Estado Libre y Soberano de San Luis Potosí is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 58 municipalities and its capital city is San Luis Potosí....
, and eastern Jalisco
Jalisco
Jalisco officially Estado Libre y Soberano de Jalisco is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is located in Western Mexico and divided in 125 municipalities and its capital city is Guadalajara.It is one of the more important states...
. Similar to Eastern group but larger in most features. Distinguishable in morphology and plumage in ~80% of specimens. There is an area of apparent hybridization in San Luis Potosi that deserves study.
- Aphelocoma wollweberi potosina