Tag Archives: House Finch

WHY DO BIRDS LAY BLUE EGGS?

Did you ever wonder why some birds, such as Bluebirds and Robins, lay blue or bluish green eggs? And just as interesting why, in some cases, Bluebirds which generally lay blue eggs, a nest may comprise eggs that are almost white?

The earliest avian eggshells probably lacked color, or pigmentation. Over time, most likely to protect the eggs from predators, birds evolved a diverse range of colored shell markings from mottled brown, gray and beige to rainbow hues from pure white to pale pink, lavender, yellow, aqua, orange, blue, born and even black.

The molecules that cause pigmentation in bird eggs are biliverdin (the blue-green shades) and protoporphyrin (red and brown colors and speckles) but we can talk about blue eggs without getting too technical.

Basically, blue and blue-green strikes a balance between white and very dark colored eggs. Darker eggs are predicted in moderate light to shield the embryo from intense light, including harmful UV radiation. If when eggs are in an exposed nest and the shells are too dark, it can cause the interior to heat up, similar to a “dark car effect.” Simply stated, blue eggs regulate the effects of sunlight on the developing chick (embryo).

This doesn’t explain entirely why Eastern Bluebird eggs range from white to blue green. Many cavity nester’s eggs are white because the adults need to see the eggs in the dark. Wood Ducks are an example of cavity nesters with white eggs. American Robins generally nest in trees or a semi-exposed site and their eggs are blue, affording both protection from dangerous UV light and low risk from heating up. Eastern Bluebirds are cavity nesters but only about 4 to 5 percent of their eggs are white. Oftentimes when learning about a topic, myriad more questions come to mind!

White Eastern Bluebird Eggs

To read more –

https://www.researchgate.net/publication/298798982_Shedding_Light_on_Bird_Egg_Color_Pigment_as_Parasol_and_the_Dark_Car_Effect

https://journals.sagepub.com/doi/abs/10.3184/175815511X13207833399666

In reading about blue eggs I thought readers would enjoy seeing the amazing speckled and pear-shaped brilliant blue egg of the Common Murre, from USFWS

Some birds with blue eggs that nest locally include Red-winged Blackbird, Gray Catbird, Snowy Egret, Great Blue Heron, Little Blue Heron, House Finch, Bluejay, Goldfinch, European Starling, Eastern Bluebird, and American Robin.

American Robin nest at a friend’s home

Both Bluebird nest egg photos courtesy Google image search

 

Cape Ann Winged Creature Update

Featuring: Brant Geese, Black-capped Chickadees, Black-crowned Night Heron, Blue Jays, Cardinals, American Robins, Mockingbirds, Savannah Sparrows, House Finches, Red-breasted Mergansers, and Common Grackle.  

Beautiful iridescent feathers of the Common Grackle.

Spring is a fantastic time of year in Massachusetts to see wildlife, whether that be whale or winged creature. Marine species are migrating to the abundant feeding grounds of the North Atlantic as avian species are traveling along the Atlantic Flyway to summer breeding regions in the boreal forests and Arctic tundra. And, too, the bare limbs of tree branches and naked shrubs make for easy viewing of species that breed and nest in our region. Verdant foliage that will soon spring open, although much longed for, also obscures nesting activity. Get out today and you’ll be richly rewarded by what you see along shoreline and pond bank.

Male Red-winged Blackbird singing to his lady love

Once the trees leaf, we’ll still hear the songsters but see them less.

Nests will be hidden from view.

Five migrating Brant Geese were foraging on seaweed at Loblolly Cove this morning.

Red-breasted Merganser Bath Time

New Short Film: The Uncommon Common Tern

What fun to encounter a small flock of terns teaching its young to fish. Nearly as large as the adults, the tubby terns cheekily squawk and demand food (shrimp I think in this case). Watch as the fledglings try to master fishing skills while the adults tirelessly guide the young on how to feed themselves.

With many thanks to Paul St. Germain, president of the Thacher Island Association, for information about the ongoing restoration of shorebirds on Thacher Island.common-tern-fledgling-feeding-copyright-kim-smith

There is nothing common about the uncommon Common Tern. They were named Common because hundreds of thousands formerly nested along the Atlantic Coast. As with many species of shorebirds, the rage for wearing fancy feathered hats during the 1800s nearly drove these exquisite “swallows of the sea” to extinction. After the Migratory Bird Treaty Act was ratified in 1918, terns began to recover.

A second major setback occurred when in the 1970s open landfills were closed, displacing thousands of Herring and Great Black-backed Gulls. The aggressive and highly adaptable gulls resettled to offshore nesting sites used by terns.

Common Terns are a Species of Special Concern in Massachusetts. Through a statewide long-term commitment of restoration, protection, and management of nesting colonies, the populations are very slowly and gradually increasing.

Former nesting sites include islands such as Cape Ann’s Thacher Island. During the mid 1950s, over 1,125 pairs of Arctic, Common, and Roseate Terns nested on Thacher Island. Today there are none.

The southern side of Thacher Island is owned by the Thacher Island Association. The northern end of Thacher Island is owned by the U.S. Fish and Wildlife Service, under the authority of the Parker River National Wildlife Refuge. These organizations are working together to restore terns and other species of birds to Thacher Island.

Beautiful Indian Summer Light

Scenes from around Niles Pond and Brace Cove October

Painted Turtle Niles Pond ©Kim Smith 2015Painted Turtle

Cattails in the wind ©Kim Smith ©2015Catinninetails in the wind

Brace Cove ©Kim Smith 2015Gulls departing Brace Cove after the storm

Great Blue heron Gull Seals Brace cove ©Kim Smith 2015Great Blue Heron, seals, and gull

https://instagram.com/p/9bZ812Dynq

See More Photos Here

Song Sparrow and Finch ©Kim Smith 2015Song Sparrow and FinchCattails in the wind -2 ©Kim Smith 2015