Monday, June 25, 2018

A Northern Cardinal Nest

Female Northern Cardinal in Arkansas, November 5, 2013.
Male -- also November 5, 2013, in Arkansas.

If you live in eastern or central North America and spend any time outside, chances are good that you’re familiar with the Northern Cardinal.  Cardinals are so common, in fact, that I confess I tend not to pay them much attention—especially if there are more unusual birds nearby.  But a couple of summers ago, a pair of these birds nested in the thorny elaeagnus shrub near the house, right outside the living room window.  Naturally, I had to pay attention to that!

The cardinals began nesting in the thorny elaeagnus shrub right around the time that the White-eyed Vireos that I wrote about previously were nearly fledged.  I first noticed the female cardinal carrying twigs in her bill to the nest site, which was a few feet higher in the shrub than the vireos’ nest had been.  This was typical behavior.  Female cardinals construct the nests and incubate the eggs, while males bring food to the females during incubation and assist in feeding the young after they hatch.  

As you can see, cardinals build their nests on top of limbs, unlike vireos, which suspend theirs from forks in the branches.  Whenever the female cardinal added new material to the nest, she bent it with her bill and pushed it into a cup shape with her feet.  The outside layers were constructed from twigs, bark, and leaves, while finer materials, such as grasses and pine needles, formed the lining.
June 19, 2016 -- Cardinal building the nest!
Checking early-stage nests too frequently can lead to the parent birds abandoning the site, so I was cautious about getting photos at that point.  By June 28, there were two eggs in the nest, but, since I had been avoiding the nest, I assumed that they had probably been there for two or three days.  Cardinals lay anywhere from one to five eggs, with two to three being more typical.

According to Birds of North America Online, incubation takes 11-13 days.  The eggs were definitely hatched on or before July 7, when I photographed the slightly downy nestlings for the first time.

By July 11, the young birds were much larger and more heavily feathered.  You can see how their bills are starting to turn dark, a characteristic of juvenile cardinals.  Their beak color doesn’t change to red or red-orange until late in the fall.

July 11, 2016
On July 14, the nestlings were nearly ready to fledge.  Although it’s difficult to determine exactly how heavily feathered the average dinosaur might have been, this is what I tend to imagine juvenile dinos looking like.  (On the anatomical level, though, modern birds and the dinosaurs from which they evolved differ very little—so I’d guess that quite a lot of dinosaurs may have had full plumage.)

July 14, 2016
I think that these cardinals fledged on July 15 or 16.  Fledging usually occurs after about nine or ten days, so this estimate seems reasonable.  You can just barely make out one of the nestlings in the center of the photo below.  That photo was from July 15, and the one of the empty nest was taken the next day.  This might have been the second brood of the year from these nonmigratory birds, but I can’t say for certain.

July 15, 2016 -- at least one young cardinal still on the nest

July 16, 2016
This cardinal nest and the young in it were from two summers ago.  There haven’t been any birds nesting in the thorny elaeagnus (or thorny olive) this year, though, since it’s only a bit above waist height at the moment.  A recent windstorm damaged the shrub, causing it to lean heavily to one side, so we pruned it.  It’s a more manageable height now, with no long shoots threatening to grow over the roof (see photo below).  In its native range in Asia, this species often “climbs” by entwining its upper branches with the limbs of the trees above it.  Although I miss being able to see birds nesting so close to the house, I don’t bemoan the fate of the thorny olive.  I intend to elaborate a little on invasive plants—including this species—in a future post.
June 22, 2016

Tuesday, May 29, 2018

Last Migration


My sister and I were walking the family dog at Mississippi State University on the afternoon of May 13.  MSU is a fairly attractive campus, with a mix of both old and relatively new buildings and a good many large shade trees.  I am used to looking up, or at least directly ahead, to find birds.  Given the fact that most birds spend a lot of time in trees and shrubs, this makes sense.  My sister, though, drew my attention to something that I otherwise might not have noticed: a dead bird on the sidewalk, in front of the campus library.

(Warning!  The images that follow may be disturbing to some.)

I immediately realized that the bird wasn’t a run-of-the-mill urban species, such as a European Starling or a House Sparrow.  After I got a close look at it, I identified it as a Louisiana Waterthrush, a species typically found near wooded streams, where it feeds on the insects and other prey that it manages to catch in streams.  It even builds its nest in or near a stream bank.  It is very much a riparian bird.  As you might guess, the MSU main campus doesn’t have much in the way of habitat for waterthrushes—the nearest bodies of water are a couple of tiny experimental ponds.  There is Sand Creek, which runs north of campus and might provide appropriate habitat, but it seems odd that the bird would have strayed so far from breeding territory in that area.  Still, that is a possibility.

Louisiana Waterthrush -- note the white belly and sparse streaking.
Maybe the bird was a recent migrant.  If so, then it was a late one.  According to Birds of Mississippi by William H. Turcotte and David L. Watts, Louisiana Waterthrushes are very early spring migrants, usually arriving in Mississippi in mid-March.  Mid-May would be an unusual time for an individual of this species to still be migrating, but stranger things have occurred.  I will probably never know.

Despite their name, waterthrushes are actually warblers, not thrushes.  Their drab brown backs, pale breasts with dark markings, and pink legs make them look somewhat like thrushes, and their habit of foraging low to the ground is also a bit thrush-like, but that’s about where the similarities end.  Actually, while waterthrushes do have markings on their underparts, those markings are not spots, as you would see on most of the North American thrush species, but streaks.  Thrushes and waterthrushes differ vocally, too, with waterthrush songs sounding high-pitched and “chirpy” in the way that most wood-warbler songs do, and thrush songs having a more ethereal, flutelike quality.  

It’s worth noting that, while the Louisiana Waterthrushes typically migrates early, its close relative, the Northern Waterthrush, is a late migrant.  Northern Waterthrushes breed in Canada, Alaska, and the upper portion of the lower 48 contiguous United States—farther north than Louisiana Waterthrushes.  They pass through Mississippi from about mid-April through May 15, according to Birds of Mississippi.  If the dead waterthrush at MSU had been a Northern instead of a Louisiana, that would have made more sense to me.  But the Louisiana Waterthrush has several characteristics that differentiate it from the Northern: the solid white throat (which is usually finely spotted on the Northern), the straight line bordering the throat (which is streakier on the Northern), the broad "eyebrow" (usually much narrower on the Northern), and the sparser and broader streaks on the breast (usually denser and finer on the Northern).  I also felt from the beginning that this bird’s bill was too large for a Northern Waterthrush, and its underparts too white.  It’s important to be careful with the latter field mark, though, since there are some Northern Waterthrushes that are very pale below, instead of the more common yellowish color.

Another view of the waterthrush.  The "eyebrow" flares out at the end.
I don’t walk at MSU often enough to have found many window-killed migratory birds (in fact, the waterthrush was the first one I’d ever seen on campus), but my sister tells me that she has seen several during the spring and fall.  Unfortunately, this isn’t at all an unusual occurrence throughout the United States.  According to a recent scientific study (Loss et al., 2014 [*ironic author name, don't you think?*]), collisions with buildings kill somewhere between 365 and 988 million birds each year in the U. S.  The reason for these collisions is that birds get fooled either by reflections—of the sky or vegetation—in the windows, or by bright lights from inside the buildings.  Interestingly (to me, at least), a majority of these collisions are at low-rise buildings, rather than high-rises.  In all likelihood, the high-rise deaths occur mainly during the spring and fall, when birds are migrating, and collisions with lower buildings are common year-round.  Also, mortality during fall migration seems to be higher than during spring migration—possibly due to larger numbers of birds at that time, many of which are juveniles hatched during the previous summer.  A great many juvenile birds do not survive their first fall migration, so songbird populations are considerably winnowed down by the time spring migration rolls around.  Some of that winnowing is normal and natural, and, as we’ve seen, some of it is a result of man-made hazards along the migration routes.  Regardless of whether the Louisiana Waterthrush my sister and I found had been a summer resident or a recent migrant, man-made structures had clearly caused its untimely end.

I decided to salvage the specimen for science.  MSU has bird collections in both the Biology and the Wildlife and Fisheries departments, and clean, intact bird specimens like this are not always easy to come by.  My sister gave me an unused dog waste bag to put it in, and we continued walking until we came upon another building-killed migratory bird: a Veery.  As I mentioned earlier, waterthrushes are not actually thrushes.  However, Veeries are thrushes (in the Turdidae family, Catharus genus), even though the word “thrush” is nowhere in their name.  This could be pretty confusing for the uninitiated!  The Veery is named for its song, which supposedly sounds like “veer, veer, veer, veer.”  Well, to be fair, it’s considerably more pleasant than that—a series of descending phrases that have a fluty, echoing quality.  Veeries are truly transients in Mississippi.  Although some can be found nesting at very high elevations in the Great Smoky Mountains, they’re generally not southerly breeders.  They’re also one of the harder-to-find thrushes in Mississippi, with the Mississippi Ornithological Society listing them as uncommon transients.

Veery
Another angle
As you can see, the spots on a Veery’s breast are very pale and blurry compared to those of most other thrushes (including Wood and Hermit Thrushes).  Veeries also have tawnier upperparts than all other North American Catharus thrushes.  This tawny coloration makes the cool gray of the flanks and belly stand out.  
 
Vague, buffy spots and very pale undertail coverts
I picked up this bird, too, and later got in touch with the Wildlife and Fisheries Department to ask if they would take the specimens.  I had given them a road-killed Eastern Screech-Owl (which I had found in my neighborhood) many months before, so I fully expected that they would be willing to take these building-killed Neotropical migrants.  They were.  While it’s a shame that these two songbirds died in such an unnatural way, the silver lining is that an educational facility gained two relatively unusual specimens for study.  

I suppose the lesson here for birders is to always be observant, because you never know what oddities you might discover.  I know that I will have to remember to keep a look out for birds in front of buildings during the spring and fall from now on!  But there’s probably a bigger takeaway in here for everyone—birders and non-birders alike: We need to do more to reduce the number of birds that are killed from collisions with buildings.  Placing various grids and patterns on windows to break up their reflections helps, as does turning off lights at night.  A study by Chicago’s Field Museum demonstrated just how effective turning off the lights can be: bird kills decreased by 83%!  Obviously, it isn’t possible to prevent all bird deaths, and people will always need places to live and work, but maybe just a little more consideration for the natural world could go a long way.




Sources and links:

- Loss, S. R., Will, T., Loss, S. S., and P. P. Marra.  2014.  Bird-building collisions in the United States: Estimates of annual mortality and species vulnerability.  Condor 116(1):8-23.  (http://www.bioone.org/doi/full/10.1650/CONDOR-13-090.1)
- Turcotte, William H., and Watts, David L.  1999.  Birds of Mississippi.  Mississippi Department of Wildlife, Fisheries and Parks.  University Press of Mississippi, Jackson.