Scientists from Cornell University are using Project FeederWatch data and observations to study the interactions of Downy and Hairy Woodpeckers.

Similar Look

Left: Hairy Woodpecker; Right: Downy Woodpecker

Click on the above image to learn how to distinguish between the two species.

The two woodpeckers look very much alike. Typically when two species look very similar to one another, it is easy to assume both species have a close evolutionary relationship. However, modern DNA analysis has shown they are not closely related.

The Hairy Woodpeckers are more closely related to White-headed and Red-cockaded Woodpeckers which look very different.

Hairy Woodpecker	White-headed Woodpecker	Red-cockaded Woodpecker
Male: Image Source	Male: Image Source	Male: Image Source

The Downy Woodpeckers are more closely related to Ladder-backed and Nuttall's Woodpeckers.

Downy Woodpecker	Ladder-backed Woodpecker	Nuttall's Woodpecker
Male: Image Source	Male: Image Source	Male: Image Source

The DNA analysis suggests there other reasons why Downy and Hairy Woodpeckers look like one another.

Testing Hypotheses with FeederWatch Data

Scientists have postulated that Downy Woodpeckers benefit from their similar look to Hair Woodpeckers.

Why? Possible reasons are:

• The "Hairy Woodpecker Trickery" hypothesis: If a Hairy Woodpecker misidentifies a Downy as a Hairy then maybe the Hairy would be less likely to chase the Downy away from food or other valuable resources.
• **The "Innocent Bystander Trickery" hypothesis: **The Downy uses its resemblance to the Hairy to fool other bird species into thinking they are the bigger Hairy Woodpecker thus chasing other birds away.

A recent study (Pecking Order at the Bird Feeder) collected data from Project FeederWatch participants to observe the interaction between birds at feeders.

Results

The data collected from Project Feederwatch observations found that Hairy Woodpeckers chased away Downy Woodpeckers from feeders at least as much as you would expect based on random encounters. This ruled out the "Hairy Woodpecker Trickery" hypothesis.

The observations determined that Downy Woodpeckers are especially dominant for their size. Downy Woodpeckers have been observed winning scuffles with Northern Cardinals which are larger than Downy Woodpeckers.

Downy Woodpecker	Northern Cardinal
Male: Image Source	Male: Image Source

The pattern of interactions between the Downy Woodpeckers and other species was subtle. More data (observations) are needed to confirm the "Innocent Bystander Trickery" hypothesis.

What's Next

Researchers at Cornell University are considering ways to test the finding in the field. One of the options under consideration is to look at Hairy and Downy interactions at feeders in the few places where these species do not overlap in population distribution. These would be areas such as Florida and parts of the Southwest in the United States. If you live in one of these areas and are interested in contributing to this research, you can sign up here before 28 February 2018.

Sources and Full Articles

Why do Downy and Hairy Woodpeckers look so similar when they aren’t close relatives?, Project FeederWatch, 19 February 2018

Downy Woodpecker and Hairy Woodpecker, Project FeederWatch

When 136 Bird Species Show Up At A Feeder, Which One Wins?, All About Birds, 8 January 2018

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