March 2024 Natural Mystery Answered

Our Tracking Club facilitators showed their skills on last month's Natural Mystery. Three of them send in answers. All were correct and one was exceptionally detailed. Congratulations to Adrian Iacovino, Kirsten Welge, and Maria Wesserle for their correct interpretation of these tracks.

These are the tracks of a Great-horned Owl, Bubo virginianus.

I'll let Adrian start off our analysis with these succinct observations:

These are big, puffy, K-shaped tracks. Toe 1 and 2 form a straight line; toe 3 and 4 form an acute angle.

As Maria notes, this means that “the straight line of the K on the inside of the track.” She then explains:

This indicates an owl species, versus woodpeckers, who also have zygodactyl feet, but the straight line of the K is on the outside of the track.

Kirsten takes this analysis a step farther, noting “there are several groups of birds with zygodactyl foot structure in North America: cuckoos, woodpeckers, parrots, osprey, and owls.” She then addresses each of these candidate groups:

As for the species, Maria notes:

The low range for great horned owl feet starts at 3.25 inches, and these tracks are well over that. Finally, Elbroch states that great horned owls are comfortable on the ground, and the paragraph above describes a 15 meter walking trail.

Similarly, Kirsten shares:

I've heard both Barred Owls and Great Horned Owls calling around neighborhoods near this park. However, the size of this track falls in the range of the Great Horned Owl: L 3.25-4.5", W 2.25-3". Additionally, this species is known for walking on the ground for long stretches, presumably to hunt small prey.

Great analyses, and spot on. This was the first time I had seen an extended walking trail of a Great Horned Owl here in Minnesota. Previously I'd only seen these out west. As Kirsten notes, Great-horned Owls are presumably walking in search of small prety--and indeed this spot was loaded with mouse tracks. 

You can read more about Great-horned Owl tracks in this Featured Track post from September, 2021.

And for a bit more of a dive, here is the iNaturalist observation for the trail these tracks came from, together with observations of some other zygodactyl tracks for comparison:

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