Saturday, December 5, 2009

Rosy-Finches

Because I just love the pink-butts, and because I had dozens and dozens in my yard the other day, I've decided to research them. This is the first of
four posts; information on the three species follow.

The order Passeriformes (perching birds)/the family Fringillidae (finches: goldfinches, bullfinches, chaffinches, siskins, canaries, cardinals, grosbeaks, crossbills, linnets, and buntings)/the subfamily Carduelinae (a larger group that contains several genera which feed their young mainly on seeds)/the Genus Leucosticte (Rosy Finches)

The Rosy-Finch is a medium-sized, chunky finch with variable pinkish color on belly, rump and wings. They are 5.5 to just over 8 inches long; their wingspan is about 13 inches and weight is 0.8 to 2.1 ounces. Sexes are similar in size and coloration, but males are more colorful. All forms of rosy-finches in North American were once merged with the Asian Rosy-Finch into a single species (1983 to 1993). However as genetic, biochemical and other evidence became available, the three distinct North American species of rosy-finch are again recognized, with Gray-crowned Rosy-Finch being the most widely distributed and abundant form. While all rosy-finches have an affinity for alpine or tundra habitat, in the US, the Black Rosy-Finch holds the middle position geographically between the Gray-crowned Rosy-Finch to the north and west and the Brown-capped Rosy-Finch to the south and east.

I couldn't stand it...I had to add a photo I found on Wikimedia: an Asian Rosy-Finch. The author mentioned how rare the bird is, that the thirty of so who came every year, became a pilgrimage too, for the Koreans who went to see them. You sure can see the resemblance.

All three populations are distinguished by head pattern, size and body color, though intermediate birds are unidentifiable. The Black Rosy-Finch is very dark brown, appearing black as a back-ground color. The Gray-crowned Rosy-Finch much lighter, browner bodied; pink to red feather margins often more extensive but contrast less with brown plumage. Brown-capped Rosy-Finches lack silver-gray on head and are much lighter and browner-bodied
…males are nearly golden.

All Rosy-Finches display some degree of pink to red on belly, rump, upper- and under-tail coverts, and on the wings, especially at the outer bend. This pink becomes spectacular ruby-red, spectral red or a geranium-color by midsummer. All have white nasal tufts, black legs and feet and dark brown iris. The tail is notched, tail and wings are long and under-wings appear silvery in flight…except for the Grey-crowned.
It seems to be likely that plant pigments are required for normal plumage color development, as in other carduelines.

All finches are known for their nomadic wandering and this certainly applies to the Rosy-finches. Because it breeds so high, little is known of this bird though it does gather in large, mobile and unpredictable flocks of mixed rosy-finch flocks. In winter, it occasionally descends to mountain and sometimes even foothill feeders and then suddenly departs. While finches are known for their erratic winter movements, roving flocks of rosy-finches are notorious for being unreliable to find at winter feeding stations. As in some other finches, rosy-finches observed to feed along salted roads (or urinated ground) and have the habit of suddenly departing and leap-frogging ahead of birds further up the road and landing again; successive waves flying over the others. They likely do this at feeders, as well.

In winter, Rosy-Finches roost in cliff crevices, mine shafts, wells, abandoned Cliff Swallow nests and around human-made structures such as in barns, under piers and in railroad cars, which provide protection from wind and reduce radiant heat loss. These birds also exhibit a mild nighttime hypothermia, like other carduelines, but not so sever as chickadees.

When driven to lower altitudes by rough weather, the Rosy seldom moves below the snowline, but remains in areas at least thinly covered by snow, even when completely snow-free areas readily available. Flocks often come to feeders at these times but are nearly absent during
fair weather and in years with less snow.

This is mainly an altitudinal migrant. Many may remain at high altitude throughout winter except when driven down by adverse weather and deep snow covering food supply, when they descend to valley until conditions improve…which is why we see them mainly in inclement weather and call them ‘snow birds’.

Migration timing depends on weather to some extent. Generally Rosies arrive on the tundra in April and leave (if they leave) around October. Individuals wintering close to mountains continue to move up and down with storms throughout fall and winter, making migratory periods indistinct. The bird sleeps at night and so probably is a daytime migrant.

As with all Rosy-Finches, bills are yellow for the winter. About the second week of February, probably in response to increasing day length, the bill begins to re-darken. Dark pigment first appears at tip and works slowly toward base.

The Rosy-Finch is a ground forager which primarily on seeds, with some other plant matter and insects; the proportion of insect-food taken increases in summer and when feeding young. They are most often seen feeding on insects and seeds on snow banks, and along their muddy, melting borders. Here, old food items are freshly uncovered, new items are deposited by the melting snow and seeds are germinating offering a nutritious bounty.

Contrary to popular belief, this bird both walks and hops. While it may walk, run and hop during a single advance, it favors
walking while slowly foraging on the ground
and hops when on snow.

One unusual behavior of all rosy-finches is that males defend ‘floating’ territories that move with their mates, rather than a fixed piece of real estate. This occurs only during the breeding season; feeding and roosting birds in winter do so often quite closely.

Rosy-Finches nest on the ground in a cup of woven grass and stems, lined with fine grass, hair, and occasionally feathers. The nest is built in crack or hole in cliff, on small cliff ledge under overhanging rocks, or under rocks in talus slides. Nests usually placed on north-facing cliffs, often overlooking snowfields or glaciers, surfaces of which are important feeding areas. . It is assumed that eggs and hatchlings of Rosy-Finches are cold tolerant, as nests are in shade and air temperatures are often below freezing at night and during storms.

Flight is strong and direct, often undulating; including during lengthy aerial displays by males. Undulating flight consists of several quick wing-beats followed by long, graceful glides, for long flights, similar to other cardueline finches. Flocks in flight are coordinated like shorebirds, wheeling and turning in synchrony. Flocks foraging on snow surface in summer or along a highway in winter often move forward in leap-frog fashion. Young birds form flocks in August, earlier than do adults.

All Rosy-Finches possess paired sacs, called buccal sacs, beneath the floor of their mouths, found only in one other North American genus (Pinicola). In addition to their crops, this added space allows parents to carry more food with each trip to the young; making longer flights cost-effective and allowing parents to search for food over a wider area… as far as 2.5 miles from the nest; a good thing in their sometimes barren environment.

Rosy-finches carry extra fat in winter; adding about three grams more than their average summer weight, which helps them survive the bitter cold where they live. The buccal sacs not present in winter, but the bird fills its crop before entering roost to provide enough energy to survive long winter nights, where ambient temperatures
are often well below minus -20F.

While these Finches were visiting my yard, I was surprised that when I went out to spread more seed, birds returned while I stood only 3-4 feet from them. They seemed very tame. Then I read that females on nests often allow approach by an observer to within a foot of them before flushing and may attempt to return to nest while nest contents are being examined. At one nest visited often, the female did not flush when she was pushed by hand from her. The apparent reason for this ‘tame’ behavior is that they breed so far from human populations and have not learned to be afraid. The broken-wing act not reported for Blacks or Brown-capped, but is known for Gray-crowned Rosy-Finch; but I don’t know that it was used during human involvement.

A group of rosy-finches are collectively known as a "bouquet of finches”.

Resources
The Sibley Field Guide to Birds of Western North America – David Allen Sibley
Smithsonian Field Guide to the Birds of North America – Ted Floyd
Western Birds – Roger Tory Peterson
Birds of North America-Online from Cornell Lab of Ornithology
WhatBird.com - Field Guide to Birds of North America – also from Cornell Lab of Ornithology
USGS.gov - Science for a Changing World

Photos are mine...except the one noted

5 comments:

eileeninmd said...

Great post and photos of the Rosy finches.

Beverly said...

Thanks Eileen...there are 3 more (shorter) pieces to follow; one for each Rosy. I hope you like them.

Hey, great shot of the Harrier. I wonder who they watch when they do that...fly alongside the car. And I agree with you on the Wood ducks being one of the prettiest! You got great shots, too.

Thanks for stopping by, again!

scienceguy288 said...

Wow, you must really like these birds. The post was very informative, thank you!

Beverly said...

SG,

Thank you so much! I had much fun, but did nearly nothing else (except feed the Rosies and other birds!) but research and write. Three more (shorter) pieces follow.

Oh, and while Rosies ARE Boreal birds (see: http://www.borealbirds.org/ )…I found nothing regarding eruptive behavior. Still, I suppose it happens.

I think this sight: http://www.rosyfinch.com/ might mention such a thing, but I couldn’t find it in the time I have (I DO need to get some other work done. LOL)

Thanks again for your kind words!

Beverly said...

SG,

Thank you so much! I had much fun, but did nearly nothing else (except feed the Rosies and other birds!) but research and write. Three more (shorter) pieces follow.

Oh, and while Rosies ARE Boreal birds (see: http://www.borealbirds.org/ )…I found nothing regarding eruptive behavior. Still, I suppose it happens.

I think this sight: http://www.rosyfinch.com/ might mention such a thing, but I couldn’t find it in the time I have (I DO need to get some other work done. LOL)

Thanks again for your kind words! And yeah...I do like the pink-butts...