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Winter 2013

Urban Jungle

The changing natural world at our doorsteps | Illustration and text by Patterson Clark      

January 1, 2013

Cardinals on high — treetop feeding from the bottom of the barrel

Winter winds strip samaras from the crown-shaped fruits of tulip trees, filling the air with thousands of winged seeds that whirl to the ground.

But on a calm, cold day, the sight of a single spinning samara might indicate that another form of seed dispersal is at work — a hungry squirrel or bird dislodging samaras while rummaging through a fruit in search of a morsel.

Usually preferring to feed on the ground or in bushes or low branches, Northern cardinals can be drawn high into tulip trees by the lure of abundant fruits.

Numerous fruits, however, don't translate into that many edible seeds. Only about 5 to 20 percent of the samaras contain viable seeds — small ones at that.

But those slim pickings are apparently worth the extra effort and exposure for cardinals, now that many of their preferred autumn fruits (such as dogwood, poison ivy and greenbriar) have been consumed.

In winter, cardinals feed together in small, loose flocks, which helps minimize the time each bird must be on the lookout for predators, crucial for when they are high up on bare branches and vulnerable to attacks from small hawks.

Sources: Ecology, Wilson Bulletin, U.S. Forest Service

tulip tree samara, liriodendron tulipifera
Northern cardinal, cardinalis cardinalis, and tulip tree, liriodendron tulipifera