The birds are shy and tend to keep well hidden.

The birds tend to exercise this ability depending upon its position relative to the outside of the flock.

The birds tend to remain within a well marked area and do not wander widely.

Dead birds tend to weigh less than in life.

The birds tend to come back to the areas where they nested previously.

Thus, altricial birds tend to be found in the most derived groups.

These are tightly packed, and the birds tend to take off together.

The best birds tend to rise above the rest of the kit to show off their talents.

The bird, probably the last of its species, was tending an empty nest.

Older birds tend to have a wider repertoire than younger ones.