A blooming ‘Winter King’ hawthorn attracts warblers

When my wife and I moved into our home in 2000 in Lansdale, Pennsylvania, she set out to create a garden that would attract birds, by planting it with native shrubs and plants.

Later, when we needed to replace a few dead or dying trees, she looked for a tree that she thought would be most suitable for the garden. After some research, she decided to plant a Crataegus viridisor “Winter King” hawthorn, the 1992 “Gold Medal Plant” designated by the Pennsylvania Horticultural Society.

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This variety of hawthorn had much to recommend it. As well as being disease resistant, it would have been covered each spring with masses of white flowers, followed in the fall by orange-red berries that birds eat. In addition to attracting birds, the tree was resistant to deer, which made it an essential choice since deer have entered our borough.

As the tree grew and the fall berries became more abundant, we were delighted but not entirely surprised to see Cedar Waxwings and Mockingbirds, occasionally joined by American Robins and Wrens. ruby-crowned, feeding on the bounty of the tree. However, what became a surprising bonus for us were the birds the hawthorn attracted each spring in mid-May, when it truly became a mass of white flowers: the warblers.

Initially, we thought the appearance of Neotropical migrants was just a fluke. After all, we live in the middle of town and our property is not adjacent to a park or a large wooded area. However, over a period of a few years, we noticed that the warblers reappeared quite predictably, especially if the masses of white flowers peaked at the right time in May.

Naturally, we began to monitor the tree more closely, which is much easier than looking for warblers in the large parks and nature reserves in our area. And since hawthorn only grows about 25 to 30 feet tall, it concentrates birds in a relatively small area.

Over the past few years, we have now documented nine species of warblers in our Hawthorn: Common Yellowthroat, American Redstart, Northern Warbler, and Yellow-rumped Blue Warbler, Black-and-White, Magnolia, Nashville, Wilson, and Black-throated Warbler.

American redstart

I noticed that some birds seem to stay for two or three days, which prompted me to do more research on this unexpected bonus from our tree. It was not difficult to find the answer. In a 2009 article in the Journal of Animal Ecology, three scientists from the Sonoran Desert Research Station and the University of Northern Arizona discussed the phenomenon we were seeing in our garden, namely “flower power”. Their paper was aptly titled “The Power of Flowers: Tree Flowering Phenology as a Settlement Signal for Migratory Birds.”

Summarizing their paper, researchers Laura McGrath, Charles van Riper III, and Joseph Fontaine pointed out that small Neotropical migratory birds such as wood warblers cannot store enough energy to make their long migration journey uninterrupted without stops. periodicals for food. Therefore, they show a clear preference for stopover habitats with sufficient food reserves.

However, it has not always been understood what cues birds respond to when selecting one habitat over another. Researchers argue that for insectivorous migrants like warblers, flowering, leaf discoloration and leaf loss associated with vegetative phenology can reliably predict the availability of herbivorous arthropods – the insects they feed on.

So it is not difficult to see the special appeal of our hawthorn. Its mass of white flowers is apparently an irresistible sign, at least to warblers passing within sight of our backyard. Indeed, with careful observation, we can see the tiny insects that warblers spot around the flowers of the tree. For this reason, when we retire and renew our garden in another location, a ‘Winter King’ hawthorn will certainly be an addition to our yard, if it is not already present.

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