Friday, November 16, 2012

Conifer: cone and Crossbills

It looks like this year is another large irruption of crossbills into the Northeast. Usually, the eruptions occur when there is decreased amount of food in their normal territories.

Crossbills feed on seeds from conifer trees. Most people feel that conifer or pine cones are the seed of the conifers or evergreens. However, conifer cones. I really a cluster of a highly modified woody scale that up tightly packed together to protect the developing conifer seeds that are inside. Crossbill's bill is designed to help remove the seed from inside the woody scale. After prying the woody scale from a cone, they will start at the bottom and crack the scale and then use their tongue to remove the seed. Just as people can be either right-handed or left-handed, crossbills bill can cross in either direction, and the direction of the bill determines the direction that the bird spirals up the cone. It has been determined that they can eat up to 3000 seeds a day.

Here is a series of photographs that shows a male White-winged Crossbill working on a scale and then obtaining the small seed out of it to eat.
Close-up of a Female White-winged Crossbill with a seed in her beak