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An owl needs dinner too

Updated: Dec 11, 2018

For first-year red-headed woodpeckers (and many other bird species), late summer represents the beginning of independence from their parents. Young birds gradually begin to forage on their own and move greater distances from the nest, exploring the environment around them. Parents often assist this process through aggressive interactions with their fledglings—as if to say "let's get a move on, time to go!"

By fall, these smaller movements shift to even larger ones and thus begins the process of natal dispersal, the manner through which immature individuals permanently depart their natal area in search of new sites. Natal dispersal is one of the driving forces behind gene flow and can have a major impact on the structure of animal populations—for instance how many individuals within a population are male, female, young, or old. These factors have long-term implications for population survival and help us understand the trajectory of a population in terms of growth or decline, which can ultimately guide management efforts.

Despite its importance, the juvenile stage is one of the most poorly understood portions of animal life cycles due to the logistical constraints of observing young after they reach independence and move from their natal site. Studying juvenile survival in red-headed woodpeckers is made somewhat easier because young can be accessed in nest cavities (assuming the nest tree is stable enough to support a ladder and the nest cavity is within reach). Radio-transmitters (or other tracking devices) can then be attached to nestlings so that they can be located once they leave the nest.

Fledgling red-headed woodpecker with radio-transmitter

Dispersal and other movements away from parents don't come without their risks. Young birds face naturally tough odds—for example less than 50 percent of young songbirds survive their first year of life. Juveniles are naive to their environment and predators of all kinds await an easy meal. Preliminary evidence from our work at Cedar Creek suggests that juvenile red-headed woodpeckers have slightly higher survival than their songbird counterparts, perhaps due to more time spent in the cavity before fledging and more parental care. Despite these potential benefits, not all young red-headed woodpeckers will make it. Tracking marked juveniles with radio-telemetry equipment is the best way to determine their fate and how they may have met their end.

This year we tracked two of our marked juvenile woodpeckers on different occasions and found their remains, including leg bands and still-working(!) radio-transmitters inside owl pellets. We suspect that the pellets were from a Great-horned Owl (or two owls with the same taste preference), given their large size.

Juvenile red-headed woodpecker remains and yellow leg band inside owl pellet

Working radio-transmitter and leg bands from juvenile red-headed woodpecker. Quarter shown for size.

Great-horned Owls are adept predators and we have seen them being mobbed by crows and other birds at Cedar Creek this summer, so it's clear that they are less than desirable neighbors for many members of the bird community. But owls—like other animals in the food chain—need to eat too and are important members of Cedar Creek's ecosystems, despite their taste for one of our favorite species.

Illustration by Megan Massa


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