September 2024 Natural Mystery Answered

Last month’s Natural Mystery proved to be a challenge. Despite the near perfect substrate, the behavior of the animal left mostly partial tracks in an unusual presentation. We received a range of guesses for, covering a spectrum of birds and mammals. Congratulations to Maria Wesserle and Kirsten Welge for correctly identifying the maker of these tracks as well as the animal’s behavior. An honorable mention goes out to John Bauhs, who correctly interpreted the animal’s behavior.

These are the tracks of a spotted sandpiper (Actitis macularius) taking flight.

Here is Maria’s interpretation of the tracks:

"I see three tracks in this photo – one that barely registers near the bottom of this photo, and two overlapping tracks toward the top. I see three smooth toes making an arrow shape, the length of which is approximately 2.5cm, width 3cm. This shape indicates shorebird. Due to the size and morphology, I believe these are the tracks of a spotted sandpiper. I don't see a hallux registering, but I think that is because of the soft substrate of the sand and the fact that the two tracks near the top of the photo are very toe-heavy. I also considered killdeer for these tracks, as they look similar and don't have a hallux. However, killdeer tracks tend to be slightly larger, and toe 3 is a bit off-center and closer to toe 4. Sandpiper tracks appear more symmetrical, which is what we see in this photo.”

Kirsten echos much of Maria’s analysis, writing:

“The symmetrical toe angles and track size strongly suggest this is a spotted sandpiper track; a clear hallux would clinch that ID. Killdeer tracks would be larger, from 1 – 1¼" in length and 1⅛ – 1⅜" in width, and would show clear asymmetry between the toes, with angles of roughly 80° between toes 2 and 3, and 45° between toes 3 and 4.”

To my eye, there is one hallux impression visible. It is at the 5cm mark, just below toe 2 of the left track. This allows us to bring even more confidence to our identification.

For the bird’s behavior, Kirsten makes this observation:

“The deep toe and claw marks and flicked up sand indicates an event with forceful movement. These are the toe and claw marks from both feet of a spotted sandpiper as it pushed forward and up to take flight.”

Maria similarly interprets the movement of the sand in this way:

“As for the behavior, we can see that there is a lot of weight in the tips of the toes and the claws in the two tracks near the top of the photo. Sand is being pushed backward, toward the bottom of the photo. I think this shows a sandpiper taking off in flight, launching themselves off into the air."

John identified the bird to the correct family, and recognized the bird’s behavior, writing:

“The bird steps or hops forward, placing mainly the nails of both feet into the sand and pushes off to fly away.”

Congratulations again to Kirsten and Maria for both identifying and interpreting these tricky tracks, to John for recognizing the behavior, and to everyone who took the time to submit an answer and share their process.

Support the Newsletter

If you enjoy these natural mysteries, please consider supporting the Minnesota Wildlife Tracking Project newsletter on Patreon or buy me a coffee.