Sam Crowe on January 5th, 2020

Which came first, the chicken or the egg?  Scientists now say that since birds evolved from dinosaurs the egg came first.  In either case bird eggs are an amazing invention.

Bird eggs begin essentially as a food sac or yolk.  The fertilized egg cell is part of the yolk and rests on its surface. It is the fertilized egg cell that grows into the embryo.

The female bird’s reproductive tract works like an assembly line. As the yolk moves along it is coated in albumen, or egg white, for protection.  Then, shell membranes, the egg shell and the shell covering (cuticle) are added.   The whole process moves along at a rapid pace, about a day in many species.

Eggs are not all the same shape as the chicken eggs that we eat. Some birds eggs are more pointed, or pyriform and, at the other extreme, some are more rounded or spherical.

Egg shape is partially determined by the internal structure of the female. Her oviduct, distribution of internal organs and shape of her pelvic bones all affect egg shape. For example, the Mallard’s egg is subelliptical (not quite a sphere). The Great Horned Owl’s egg is spherical and the Red-tailed Hawk’s egg is elliptical. Other eggs are more pointed.

The shape of an egg’s hell does affect its physical properties. The general spherical shape of an egg maximizes shell strength. The more rounded an egg is the eggs the volume it has for the amount of egg shell produced.

In some species the shape of the egg has evolved over time to fit into the nesting environment.

Shorebirds usually lay four eggs that are somewhat pointed.  The adults orient the eggs so the pointed end points to the center of the nest.  This approach minimizes the amount of space needed for the nest.

Cliff-nesting birds also lay pointed eggs.  For example, Common Murres lay one egg on a bare nesting ledge. If the egg is bumped it will tend to roll in a circle instead of rolling off the edge.

Bird egg collecting, known as Oology, was once a major source in the decline of many different birds.  Fortunately it is now illegal to collect the eggs of all native North American birds.  Egg collecting is banned in many countries but is still practiced illegally.

The British seem to be especially active in the now illegal hobby. Brit Colin Watson was one of the world’s most notorious egg collectors and specialized in the eggs of rare and endangered birds.  He fell to his death when climbing a tree in 2006. Supposedly he maintained a list of 300 fellow egg collectors.

In 1997 two Brits were fined 90,000 pounds each for collecting the eggs of protected species.

in June of 2016 another Brit was also arrested and fined for collecting the eggs of the Arctic Tern and Great Skua.

Sam Crowe on December 21st, 2019

The beautiful Aplomado Falcon was once extinct in the United States. Re-introduction efforts in far south Texas are being successful.

Aplomado falcons are most often seen in pairs. They do not build their own nests, but use stick nests built by other birds. Pairs work together to find prey and flush it from cover. Aplomados eat mostly birds and insects. They are fast fliers, and often chase prey animals as they try to escape into dense grass. Parents make 25-30 hunting attempts per day in order to feed their young. Chicks are fed 6 or more times each day. They live up to 20 years in captivity. Falcons are being reintroduced in south Texas to bring back the population.

Information from the Texas Breeding Bird Atlas

Information from Texas Parks and Wildlife

Sam Crowe on December 14th, 2019

The majestic Golden Eagle is not as wide-spread as the better known Bald Eagle, at least in the United States. It is, however, found in Europe and Asia.

The Bent Life History Series has this to say about the Golden Eagle.

Golden Eagle. © Glenn Bartley

“This magnificent eagle has long been named the King of Birds, and it well deserves the title. It is majestic in flight, regal in appearance, dignified in manner, and crowned with a shower of golden hackles about its royal head. When falconry flourished in Europe the golden eagle was flown only by kings. Its hunting is like that of the noble falcons, clean, spirited, and dashing. It is a far nobler bird in every way than the bald eagle and might well have been chosen as our national emblem. But then the golden eagle is not a strictly American bird, as the bald eagle is.”

Sam Crowe on December 8th, 2019

The annual Audubon Christmas Bird Counts are now in their 118th year.   The counts are a fun way to get outside and do a little counting for the birds.  All skill levels are invited and there is no cost to participate.

Visit the Audubon web site to find a location near you.

Bl.ue Jay

Blue Jay

Sam Crowe on November 30th, 2019

Enormous hazards face birds even before they hatch. Although the odds against one individual bird appear staggering, avian species as a whole survive well, except where they are threatened by the man-made effects of environmental destruction or poisoning.

The life span of most birds in the wild may be no more than six months to a year or two.  Generally, larger birds have longer life spans – wild Canada Geese have lived over 18 years and Golden Eagles for 30.

Among medium-sized birds, cardinals have lived in the wild for 10-12 years and robins for 17.

Male Northern Cardinal (Cardinalis cardinalis) perched on a branch in Southeastern Ontario, Canada.  © Glenn Bartley.

Chickadees and goldfinches are known to have survived for 8 or more years in the wild.  Keep in mind that these are not the norm, since the stresses of disease, injury, migration and winter starvation take enormous tolls, particularly on young birds during their first year of life.

Bird banding studies are one of the ways scientists are able to determine bird life spans and sometimes even the age of a particular bird.  The USGS web site has excellent information on bird banding.  Both professionals and trained amateurs band birds. This page has information on the longevity record for many species.  

Sam Crowe on November 23rd, 2019

The small Bufflehead is one of my favorite ducks. It also a favorite of others, as witnessed by this description of the Bufflehead as described in the Bent Life History Series.

Bufflehead (Bucephala albeola) flying in Victoria, BC, Canada.  © Glenn Bartley.

“The propriety of applying the name ” spirit duck” to this sprightly little duck will be appreciated by anyone who has watched it in its natural surroundings, floating buoyantly, like a beautiful apparition, on the smooth surface of some pond or quiet stream, with its striking contrast of black and white in its body plumage and with the glistening metallic tints in its soft fluffy head, relieved by a broad splash of the purest white; it seems indeed a spirit of the waters, as it plunges, quickly beneath the surface and bursts out again in full flight, disappearing in the distance with a blur of whirring wings.”

Sam Crowe on November 10th, 2019

The Hawkwatch season in the U.S. is starting to wind down.  The Corpus Christi, TX hawk watch has recorded 30 raptor species and over 500,000 individuals.

osprey in flight

Osprey with fish. © Greg Lavaty

The champion hawk watch site is at Veracruz, Mexico, where single day accounts can exceed over 350,000 Broad-winged Hawks in a single day. 

Sam Crowe on October 26th, 2019

The large Brown Jay was once somewhat regular along the lower Rio Grande River in far south Texas.  Never common, the rare visitor seems to have retreated back across the Rio Grand and has become a Texas review species.  Several years ago I shot this short video of Brown Jays feeding on orange halves and marshmallows a little south of Falcon Lake.

Sam Crowe on October 19th, 2019

As more ducks are starting to show up in their winter homes it is a good time to review duck and waterfowl identification.  The Birdzilla.com web site has an excellent section on Waterfowl Identification.

blue-winged teal in flight

Male Blue-winged Teal

Sam Crowe on September 29th, 2019

What causes a bird to start migration?  The Germans call it “zugunruhe” or migratory restlessness.  There are several factors that influence the beginning of migration, including the amount of daylight. 

Northern Flicker

Northern Flicker.  Northern Flickers are arriving in their winter homes in the southern U.S.

How birds find their way is a trickier manner.   A researcher at Cornell University used Indigo Buntings to study the migration urge and migration direction.  The buntings were exposed to a normal night sky and their behavior studied.  The birds headed south.  The night sky was then rotated.  In response the birds started moving in the direction of the “new north.”  It seems Indigo Buntings and other species use the stars to navigate.  Pretty smart, huh?