Ghiandaia delle boscaglie di Woodhouse

Identificazione

Woodhouse's scrub jay is a medium-sized bird, approximately 27–31 cm (11–12 in) in length (including its tail), with a 39 cm (15 in) wingspan, and about 80 g (2.8 oz) in weight. The species has a blue head, wings, and tail; a gray-brown back; and grayish underparts. The throat is whitish with a partial blue breast band ("necklace"). The call is described as "harsh and scratchy". Compared to the California scrub jay, Woodhouse's has a duller blue, darker gray underparts, a less distinct blue necklace, and a straighter bill.

Tassonomia

Nome scientifico

Aphelocoma woodhouseii

Autorità

(Baird, SF, 1858)

Ordine

Passeriformi

Famiglia

Corvidi

Genere

Aphelocoma

Areale e habitat

True to its name, Woodhouse's scrub jay inhabits areas of low scrub, preferring pinon-juniper forests, oak woods, edges of mixed evergreen forests, and sometimes mesquite bosques. Woodhouse's scrub jays are very common west of the southern Rocky Mountains, and can be found in scrub-brush, boreal forests, and temperate forests.<p>Woodhouse's scrub jays usually forage in pairs, family groups, or small non-kin groups, outside of the breeding season. They feed on small animals, such as frogs and lizards, eggs and young of other birds, insects, and (particularly in winter) grains, nuts, and berries. They can be aggressive towards other birds, for example, they have been known to steal hoarded acorns from Acorn Woodpecker granary trees.<p>Woodhouse's scrub jays, like many other corvids, exploit ephemeral surpluses by storing food in scattered caches within their territories. They rely on highly accurate and complex memories to recover the hidden caches, often after long periods of time. In the process of collecting and storing this food, they have shown an ability to plan ahead in choosing cache sites to provide adequate food volume and variety for the future. Woodhouse's scrub jays are also able to rely on their accurate observational spatial memories to steal food from caches made by conspecifics. To protect their caches from potential 'pilferers', food storing birds implement a number of strategies to reduce this risk of theft. Western scrub jays are also known for hoarding and burying brightly colored objects.[citation needed] Woodhouse's scrub jays have a mischievous streak, and they are not above outright theft. They have been caught stealing acorns from acorn woodpecker caches and robbing seeds and pine cones from Clark's nutcrackers. Some scrub jays steal acorns they have watched other jays hide. When these birds go to hide their own acorns, they check first that no other jays are watching. Western scrub jays sometimes land on the backs of mule deer to eat ticks and other parasites present on the deer. The deer seem to appreciate the help, often standing still and holding up their ears to give the jays access. The scrub jay even will eat peanuts off a human hand.[citation needed]<p>Recent research has suggested that Woodhouse's scrub jays, along with several other corvids, are among the most intelligent of animals. The brain-to-body mass ratio of adult scrub jays rivals that of chimpanzees and cetaceans, and is dwarfed only by that of humans. Scrub jays are also the only non-primate or non-dolphin shown to plan ahead for the future, which was previously thought of as a uniquely human trait. Other studies have shown that they can remember locations of over 200 food caches, as well as the food item in each cache and its rate of decay. To protect their caches from pilfering conspecifics, scrub-jays will choose locations out-of-sight of their competitors, or re-cache caches once they are alone, suggesting that they can take into account the perspective of others.<p>The chicks start off fully gray. The older they get, the more they turn blue. On their heads, chicks tend to have a red crest that resembles a comb (Mostly seen on chickens). The chick will lose its crest at day seven, just like the way the baby chickens lose their egg tooth at 5–7 days. Nests are built low in trees or bushes, 1–10 m (3.3–32.8 ft) above the ground, primarily by the female, while the male guards her efforts. The nests are sturdy, with an outside diameter of 33–58 cm (13–23 in), constructed on a platform of twigs with moss and dry grasses lined with fine roots and hair. Four to six eggs are laid from March through July, with some regional variations. There are two common shell color variations: pale green with irregular, olive-colored spots or markings; and pale grayish-white to green with reddish-brown spots. The female incubates the eggs for about 16 days. The young leave the nest about 18 days after hatching.