Neither its common name nor the scientific one leave no doubt of their appearance, beak with cross jaws. It is the first thing that catches the attention of this robust bird about the size of a house sparrow, and it is of the most specialized peaks of European birdlife, the cross makes its peak a perfect instrument used as pliers to open the cones and reach the pinions up that are the majority of its diet. Curiously newly hatched chicks have right peaks but in a few weeks of age curve to cross either left or right, depending on the specimen.
This animal is surprising, the plumage is so capricious that it is difficult to see two birds are exactly alike, but they have similar patterns: males are reddish with different shades (red, yellow and/or orange); being easy distinguishing between males and females, even among young ones who are olive brown with plenty spotted.
Its breeding season is also an adaptation to its diet, it does not really matter what time of year while there is a good cone production. For this reason we can see breeding pairs in the end of summer or chicks in winter.
Also the molt is a mystery because it doesn´t follow an established order, there are some adult crossbills who shed from August to October, but others can begin to shed in spring and stop in autumn. The young ones made a partial shed and quite variable, from individuals who change most of the coverage and other who just change a few of the body, being able to see the head patched with Adult color, evidently they will follow a different pattern of shed as what time they were born.
It is a very gregarious bird is easy to see them in groups of 10 or 20 specimens, mixed flocks of young birds, males and females, even now couples who are in zeal continue to provide food to the couple or feeding the chickens, without any fights or disputes on the side.
Closely linked to the coniferous forests, related to their diet so specialized, it has benefited the reforestation of Aleppo pine (Pinushalepensis) as in the Sierra Sur of Seville, specifically in the Sierra del Becerrero, where it is the emblem of the Ornithological Station of the Snake Refuge, being a very rich and unique population in the province of Seville, which delight photographers who enjoy delHide available in this natural space. Curiously average in a day of bird ringing which are sampled 100 birds, 50 are crossbills.