Much smarter than a fifth grader

There is no doubt about it — Cowbirds exhibit ingenious methods of manipulating other bird species into raising their little brown-headed offspring.   Cowbird eggs have been found in the nests of 220 bird species, ranging in size from hummingbirds to raptors.

By watching the nesting activities of particular target bird species, Brown-headed Cowbirds time their reproduction with that of their host, forcing the host to raise their chick for them.  A single female, laying just one egg in a host nest, may produce up to 36 eggs in a breeding season.

Cowbird chicks are usually larger than the host species chicks, hatch a little earlier, and grow a little faster, so they may consume the bulk of the food that parents bring to the nest, to the detriment of the host’s own chicks.

The end result is a single large Cowbird chick that follows its host parent (in this case, a Chipping Sparrow) around incessantly begging for food.

Some species, such as Robins, Gray Catbirds, and Brown Thrashers, physically eject cowbird eggs from their nest and seem less susceptible to nest parasitism. Blue-gray Gnatchatchers desert their nest if they find cowbird eggs in it and Yellow Warblers simply build another nest on top of the one that was parasitized, hoping the cowbirds don’t find them again.

However, Cowbirds have learned to retaliate against some egg rejectors with “mafia-like” behavior.

Ever watchful, Cowbirds not only monitor the nesting activity of the host, but watch what becomes of their eggs in the host nest.  If the host rejects the foreign egg, cowbirds return to the nest and destroy the host eggs!

And the “mafia” behavior works.  Prothonotary Warblers that rejected cowbird eggs managed to raise only one chick because cowbirds punctured the other eggs or threw the host’s offspring out of the nest,  Those that tolerated the presence of a cowbird chick in their nest raised three of their own chicks.  So, it pays to be tolerant of a nest parasite if you’re a Prothonotary Warbler.

Cowbirds have even learned to “farm” their host species by manipulating the hatch time of host eggs to match their own chick’s hatch time.  This is achieved simply by destroying those host eggs in the nest laid earlier than their own.

Who knew that becoming an accomplished nest parasite required such intelligence?

They do sing!

We have lots of Dark-eyed Juncos in Minnesota during the fall and spring as they are migrating from breeding areas in Canada to wintering sites in Mexico, but they are always mute.  I have never heard a Junco sing, so I was ready to look for a warbler singing a trilling song in Griffith Park the other day, when I discovered it was instead an Oregon Junco.

In fact, they sing a lot during their breeding season!

The western subspecies of Oregon Junco is browner than ours but has the same pink bill and white outer tail feathers as the migrant Juncos that move through the Midwest.  It’s nice to finally hear what they sound like!

Among the giants

Big Basin Redwoods State Park is home to some of the tallest trees in the world, the coast redwood, Sequoia sempervirens.  These giant evergreens live up to 2000 years, and grow to more than 300 feet in height and 60-70 feet in circumference.

Photos just don’t capture the immensity of their size, unless compared with something more familiar (like a person).

My grandson climbed a downed branch for a “higher” view of the redwood.

Even looking up to the tops of the trees 300 feet away doesn’t convey their immense size accurately.

How about the size of that branch that has fallen?

Big Basin state park preserves 18,000 of the once 2 million acres that covered the western slopes of the outer coast range of northern California and southwestern Oregon.  The trees only grow here because of the reliable moisture provided by coastal fog, and their great height creates a cool micro environment in which younger trees can become established.

Giant tree-like azaleas thrive in the moist, cool micro environment of the redwood forest.

The campaign to save the redwoods begun in the late 1880s launched redwoods state park as the first in California, and was instrumental in protecting these trees from the lumber industry boom following the building spree during the California gold rush.

The tallest redwood today measures 379.3 feet, but even taller giants were cut down in the 1800s; one was recorded at 424 feet in 1886.  Is there a limit to how tall trees can get, you might wonder?  As David Attenborough has pointed out in his series on the Private Life of Plants, plants must get water and nutrients to the tips of their branches, in complete silence, without the aid of mechanical pumps–relying only on the cohesive properties of water to rise in a capillary tube (the tree’s vascular network) aided by evaporation of that water from its leaves.

For a truly impressive look at the entire length of a living tree, click on the video below to take a tour of one of the world’s tallest trees.

California natural history

I haven’t visited the Los Angeles natural history museum since I was a kid, but I rediscovered what a wonderful educational place it is.  Their native wildflower garden was spectacular, complete with narrative hints on how to promote pollinators.

The bees actually preferred the north side of this bee hotel where many of the holes had evidence of larval residents.