I have seen pink-eared ducks (singly and in pairs) in Australia use vortex feeding and filtering. The rotational action concentrates prey in the center of the vortex for more efficient feeding. Phalaropes are also known for vortex feeding, but they then use their bills to pick out individual planktonic items.Ditto on the fabulous images - thanks as always for sharing!
When I see shovelers engaged in the circling feeding behavior, I call that doing the "rotifer roundup". I've seen crop samples from a shoveler food habits study that were gorged with almost microscopic rotifers. As Steve mentions, they have fine lamellae and commonly feed on rotifers, copepods, anomopods, and other tiny critters.
Greenwing teal (smallest North American puddle duck) can also forage on small food items but they are mostly vegetarian (especially small seeds) while on the wintering grounds. Like other puddle ducks, their intake of invertebrates increases later in winter and spring as they pack in protein for migration, egg laying and brood rearing.
Three of us had just launched our various pontoons or pram at Leighton Lake (BC). I'd anchored up a few dozen yards from the launch to get one of my rods fully rigged when two families of Canadian geese swam by, the goslings were maybe 1/2 the size of their parents except for one runt gosling that was bringing up the rear of the swimming birds. The two families swam ashore with the runt sturggling to get up a steep bank. About that time several ravens congregated in nearby trees making a heck of a racket. Suddenly a couple ravens swooped down and attacked the small gosling, the adult geese flared up to defend the little bird - that worked for a few seconds until several more ravens swooped down. It seemed as if the ravens were distracting the adult geese so the birds attacking the gosling could finish the kill. The gosling was killed and pretty much torn up at the edge of the lake, the geese moved on. Feast time for some noisy ravens.Crows visit my bird feeder which is a plastic tabletop. On occasion, I see them on my backyard neighbors' roof eating something small. I hope it is not hummingbirds.
@CabezonNisqually Wildlife Refuge, December 2023, Part 4 of 5
In summer, many species of the insectivorous birds are active in the early morning and just before sunset with a siesta at midday. But in winter, they sleep-in and wait for the temperatures to rise. They seem to forage first in the trees hits by the rising sun. At the end of the day, they forage in the last trees hit by the setting sun.
In summer, the flocks are more localized and smaller, an adult pair and their fledglings perhaps. But in winter, multiple families will join up and the flocks will include multiple species. Common mixes in winter include black-capped chickadees and chestnut-backed chickadees who will search from the trunk to the thinnest branches.
Often you might find a lone brown creeper climbing up the tree trunk in the middle of the group.
One or two ruby-crowned kinglets may add their frenetic energy to the flock.
On occasion, you can find a downy woodpecker in the mix as well.
Flocks of golden-crowned kinglets will cover the same territory, but they will not consistently join the chickadees. These are some of the tiniest non-hummingbird species in North America at 4-8g (3 dimes = 6.8g…).
A passing flock can be recognized by their distinctive high-pitched “tsee” calls that maintain flock cohesion. Like the ruby-crowned kinglets, these birds are always on the move.
Steve