FJ4

Date - March 21, 2021
Start time - 9:30 am
End time - 11:00 am
Location - Burlington Waterfront along the bike path
Weather - temp: 45° F, wind: 2-5 mph, precipitation: none, 0% cloud cover
Habitat(s) - sandy/rocky shoreline, urban, and some marsh

Walking up the bike path to meet the group at Echo, the first thing I noticed was a couple of Northern Cardinals calling back and forth at each other across the path. As I listened, I picked up on small differences in their calls as they went back and forth - namely differences in the length of the long "what" notes at the beginning of each call. I'm not sure what this means, but it was clear they were communicating over something. I also heard a lot of Canada Goose calls as they flew overhead in V formation in groups of 10+. I believe they honk in an attempt to keep the V formation together, which makes the long migratory flights less energetically costly for the group as a whole.

Two species that I saw a lot of today were Mallards and Ring-billed Gulls. I find it interesting that in some species like the Mallard, the plumages of males and females are dramatically different, but in other species like the Ring-billed Gulls, the plumages of males and females are practically identical. Male Mallards have a very distinct iridescent green head and females are mottled brown across their body. This sexual dimorphism is likely because the males have to attract females with their elaborate coloration - which could be explained by either the handicap principle or sexy son hypothesis. Mallards form breeding pairs in the fall and then migrate together, only parting ways after breeding season. This is something I observed today - all the Mallards I counted were in even numbers.

Ring-billed Gulls on the other hand look exactly the same for males and females. There is likely some type of coloration in the plumage that their ultraviolet-sensitive eyes can pick up on that we can't see. There are only a couple of similarities between the plumages of these two species. They both have black wing-tips which are colored with melanin to provide better structural support. They also both have featherless legs and feet, instead, they have a scaley material that provides better protection for all the uses of their feet. Countercurrent exchange allows them to maintain a warm body temperature despite a lack of insulation in their feet.

Many of the birds I saw today, mainly the ducks, gulls, and geese, were sitting in the water along a part of the shore where the surface ice was melted. Since there were a ton of them in a very shallow area, my guess is that they were simply resting during migration. This is the time of year for it (given circannual rhythms) and it was clear they weren't there to forage for food. Many of these species, such as Canada Geese, will travel with other species during migration, so it makes sense to see such a diverse group doing so. My only question is why they would be resting during the day rather than at night.

Mini Activity- Spishing:
We scared away a few Common Grackels and American Goldfinches with our spishing. While the sound can stress them out, birds are also often curious about it. Black-capped Chickadees particularly can be interested in the sound, and many other species tend to form mobbing groups around them. Small birds will flock around the sound to see if it is coming from a potential threat.

Posted on March 21, 2021 08:26 PM by grady_jakobsberg