As we at Evergreen Audubon determine when and where our bird walks will occur, we generally try to anticipate what the weather will be like and where the potential avian action might be. When I picked South Platte Park as potentially a good mid-October destination, I was thinking we would be in the midst of Indian Summer – warm days and chilly nights, but that didn’t quite happen this year as we ended up with hot days and mild nights. Consequently, migratory movement took a bit of a hiatus, and, in particular, we saw very few waterfowl on our walk. Just a reminder that during summer we can count on the possibility of seeing about ten duck species locally, but then, in the winter that number can double and during fall migration there are about twenty-six possible duck species. How many did we have on our walk on October 15? We had four duck species. What????
Let’s take a look at possible factors leading to such low numbers in the middle of fall migration. First of all, of course, has been the unseasonably warm, dry weather. But is that the whole story? Generally, with each 1°F temperature decrease the probability of migration increases by about 15%. Recently, that doesn’t seem to have been a factor. Similarly, snow-depth can promote migration, cloud-cover and precipitation can impede it, but warm weather seems to be the determining factor this year. Additionally, while photoperiod (or day-length) can stimulate hormones that influence migration the weather seems to have even over-ridden or negated that impetus. Maybe, there are ample food resources up north and that’s keeping birds from flowing down our way. Who knows? In this same vein, October is the peak month for Sandhill Crane migration, but thus far, I’ve heard of no really significant flock movement – some reports of a hundred or so birds, but nothing huge.
Sticking with the ducks just a bit longer, we had a good time checking out the color of the wings in a couple of Green-winged Teal. As you know (at least I hope you know this) Mallards generally appear to have green heads, but this is just a factor of the sunlight hitting their black iridescent head feathers at a certain angle. From a different perspective these same feathers can appear purplish-blue. The same is true for the head of a Green-winged Teal which mostly appears to have a wide green swoop extending from the eye to the back of the neck, but this swoop can look purplish in the right light. Additionally, Green-wings have an iridescent green speculum, hence their name, and which, as we saw on our walk with a different light angle, can sometimes appear cerulean (see Bill Davis’s photos).
As for the real highlight of the day, we were fortunate to see a Common Yellowthroat. These guys can potentially be around until the end of October, but they tend to have mostly moved south much earlier in the month.
South Platte Park-Oct 15, 2024
33 species
4 Participants
Gadwall 21
American Wigeon 5
Mallard 35
Green-winged Teal 4
Pied-billed Grebe 2
Rock Pigeon (Feral Pigeon) 7
Eurasian Collared-Dove 4
Mourning Dove 2
Killdeer 2
Ring-billed Gull 1
Double-crested Cormorant 6
Great Blue Heron 1
Bald Eagle 2
Red-tailed Hawk 6
Belted Kingfisher 4
Downy Woodpecker (Eastern) 1
Northern Flicker 10
American Kestrel 1
Blue Jay 2
Black-billed Magpie 9
Common Raven 2
Black-capped Chickadee 12
Bushtit 7
European Starling 9
American Robin 2
House Finch 32
American Goldfinch 62
Dark-eyed Junco 1
White-crowned Sparrow (Gambel’s) 5
Song Sparrow 6
Spotted Towhee 1
Red-winged Blackbird 54
Common Yellowthroat 1