Considering the Christmas Bird Count

American Coots (Lake Fayetteville, Arkansas, November 27, 2014)

The 101st Christmas Bird Count, back in December 2000, was my introduction to both my local Audubon Society chapter and the wider world of birdwatching.  Prior to that experience, I had birded mostly around my own yard in rural Mississippi, and certainly didn’t know anyone else who shared my avid interest in birds.  But all of that changed.  The count leader assigned my mother (who did the driving) and me to an area that included a portion of the local reservoir and dam, as well as the neighborhoods adjacent to it.  I remember standing at our first stop on the route, shivering in my heavy coat and thick gloves as I observed Bufflehead ducks and American Coots bobbing in the waves near the spillway.  Fortunately, the temperature increased considerably as the day progressed, as did the numbers on my bird checklist and my appreciation for this challenging but enjoyable form of citizen science.  What had originally been only a hobby for me was now a way to make a real contribution to ornithology.

The Christmas Bird Count is one of the longest-running wildlife censuses.  The period of December 14, 2017 through January 5, 2018 marks the 118th time that the count has been conducted.  Like many birdwatchers, I’ve already participated in my local CBC this year.  Some hardworking people will even be involved with more than one count.  The count circles, of which there are several per state or province, measure 15 miles in diameter, and each count compiler assigns portions of the count area to the various groups or individuals to cover.  The rules for counting are fairly simple: all observed, identified wild birds should be included in the tally, and the same area cannot be surveyed more than once.

American Kestrel seen on Noxubee NWR CBC, December 17, 2016

In addition to being a fun time in the field, the Christmas Bird Count is a great way to touch base with other birders and hone one’s birding skills.  While I normally do make an effort to keep accurate tallies of birds that I observe, the CBC forces me to pay even closer attention to what I’m seeing and hearing—to locate and identify every individual bird that I possibly can.  A lot of CBC work involves intensely focusing on details: listening carefully to detect all of the brief contact and alarm calls from sparrows, kinglets, warblers, chickadees, titmice, wrens, nuthatches, and creepers in the dense woods; scanning distant rafts of waterfowl for subtle differences in plumage between species; trying to get a reasonable estimate of the number of individuals in an enormous flock of blackbirds, robins, or waxwings; and so forth.

One of the most common songbirds seen in the winter months in North America: the White-throated Sparrow.  (Fayetteville, Arkansas)

The Christmas Bird Count began in 1900 as a response to the then-common “side hunts” that involved teams of hunters competing to see who could shoot the most animals—birds included—on Christmas Day.  The count’s founder, Frank M. Chapman, was a prominent ornithologist and conservationist who (quite understandably) found the tradition of “side hunts” to be irresponsible and repulsive, so he recruited a number of colleagues from all around the country to count all of the birds that they could find on Christmas.  Although the CBC has expanded considerably since its conception, its basic formula hasn’t changed much.  The fairly simple, straightforward rules make it just as fun for beginners as it is for those who have done it for years.

Considering how simple the CBC really is, how valuable could its results be to ornithology?  In some cases, more valuable than one might think.  For example, Niven et al. (2004) used CBC data to examine population changes in the bird species that breed in the boreal forests of Canada and Alaska and winter farther south.  Some of these boreal species, such as Merlins and Palm Warblers, showed population increases.  Populations of several other species were relatively stable, while some species, including Harris’s Sparrows, Rusty Blackbirds, and Northern Shrikes, had declined significantly.  The researchers noticed that the CBC winter population trends paralleled those in the data from the Breeding Bird Survey, another long-running bird census.

Merlin at Choctaw Lake, MS, December 31, 2015.

Like the authors of the boreal species study, Link et al. (2006) found that CBC data matched data from other surveys very well.  In this instance, American Black Ducks showed similar population changes on both the CBC and the Midwinter Waterfowl Inventory—an indication of the general accuracy of CBC data!  The data can also be useful for examining the impact of disease on bird populations; in 2003, C. Caffrey and C. C. Peterson looked at CBC results over a multi-year period for several common species in the northeastern U. S., and came to the conclusion that West Nile Virus had likely not significantly affected the populations in that region.  And these studies are merely the tip of the iceberg; CBC data can be a treasure trove of information for a patient researcher.  This is something worth celebrating about the CBC as the 118th count continues over the next week and as we move into a new year.

A rare (for the region) Palm Warbler seen on Noxubee NWR CBC, December 16, 2017.

References:

Caffrey, C. and Peterson, C. C.  2003.  Christmas Bird Count data suggest West Nile Virus may not be a conservation issue in the northeastern United States.  American Birds 57:14-21.

Link, W. A., Sauer, J. R., and Niven, D. K.  2006.  A hierarchical model for regional analysis of population change using Christmas Bird Count data, with application to the American Black Duck.  The Condor 108:13-24.

National Audubon Society, Christmas Bird Count Compiler Resources.  Retrieved December 30, 2017, from http://www.audubon.org/christmas-bird-count-compiler-resources.

Niven, D. K., Sauer, J. R., Butcher, G. S., and Link, W. A.  2004.  Christmas Bird Count provides     insights into population change in land birds that breed in the boreal forest.  American Birds 58:10-20.

Weidensaul, S.  2007.  Of a Feather.  Harcourt, Inc., Orlando, Florida, USA.

Noxubee from New Angles

I’ve written before about the fascinating place that is Sam D. Hamilton Noxubee National Wildlife Refuge.  The two afternoons that my family and I spent there this November definitely attest to the refuge’s uniqueness.  Our first excursion this month occurred on the 4th.  The daytime temperature was in the mid-70s, so it was hardly surprising that we saw three alligators almost right off the bat.  Being ectothermic, these reptiles can’t internally regulate their body temperatures, and instead rely on the external environment for heating and cooling.  The first two gators of our day were in the shallows of Bluff Lake, basking in the afternoon sun.

Large alligator

Larger alligator!

This smaller alligator, which was basking in the spillway, looked like a silvery bit of debris or a half-submerged log in the calm, murky water.

I like how the cypress foliage in this photo reflects on the water's surface, adding rusty hues to the muddy green.

A quarter-sized (including the leg span) orb-weaver spider seemed to float in midair as it built its web between a road sign and some nearby vegetation.

Great Blue Herons and a couple of Great Egrets foraged in Bluff Lake.  Hopefully, they were wary of the alligators!

It was nearly dark by the time we arrived at Goose Overlook, an observation platform over part of Bluff Lake, but there was still light enough for us to watch a very large cottonmouth wind its way through the shallow water.  Unlike the nonvenomous water snakes, which swim with their bodies submerged and their heads sticking out of the water, cottonmouths swim with their bodies parallel to the water’s surface.

In addition to the various chirps and chips of forest and marsh songbirds and the barking of the Canada Geese that were settling in for the night, we heard the sonorous Hoo hoo hoo hooooo hoo of two Great Horned Owls.  Visitors are not allowed to be on the refuge trails after dark, so we made the most we could of the waning daylight before packing up and heading out.  Only a few minutes before we left, I attempted a Barred Owl impression (Who cooks for you?  Who cooks for YOU-all?) and was delighted when a real one called from deep in the swampy woods.  Had the owl really responded to my noise, or was it just coincidence?  I suspect the latter, but it was nevertheless a fun incident.  Remember the Barred Owl—it will be significant later on.

Goose Overlook, November 4

Here is a picture of Goose Overlook on a different date: November 22.  Obviously, it was a different time of day, as well, and the forest birds—including Red-bellied Woodpeckers, Northern Cardinals, Carolina Chickadees, and Golden-crowned Kinglets—chattered away much more noisily.

One of my sisters drew my attention to a Wilson’s Snipe feeding in the mud.  This chunky shorebird is commonly found in marshy areas during the winter in Mississippi.

There were other good birding spots on this day at Noxubee, including Cypress Cove, where we saw a Belted Kingfisher.  The rust-red band across the belly marked this one as a female.  The male lacks the reddish band, but, like the female, it has the blue chest band.  True to their name, kingfishers are master hunters, diving into lakes and ponds to catch fish with their spear-like bills.

An American Kestrel darted up to the top of a cypress snag at the Cove.  This was a male kestrel, as you can tell from the slate-blue wings and the prominent dark bar near the end of the tail.  Kestrels tend to bob their tails when perched, and that is exactly what this bird was doing.  I noticed that most of the songbirds in the area became very quiet when this small falcon made its appearance.  Kestrels feed primarily on small birds, rodents, and insects.

We greatly enjoyed our visit.  As we headed out of the refuge at about 4:00 p.m., a Barred Owl flew in front of our van and landed in an oak tree on the side of the road.  Wow!  This was even more interesting than the aural encounter with an owl of the same species during the last visit.  The owl seemed nonchalant about our presence, sitting still and allowing us to take several photographs.  Eventually, we had to leave, but our afternoon could not have ended on a better note.  Of course, days like this are the normal state of things at the fascinating Noxubee NWR.

Sharp-shinned and Cooper's Hawks

It’s a good thing that we birders are not songbirds ourselves.  If we were, the great admiration that we have for hawks, eagles and falcons would be replaced by feelings of fear and dread at the smallest glimpse of one of these magnificently fierce predators.  And no other raptors strike fear in songbirds so much as the accipiters, a family of long-tailed, agile, mostly bird-eating hawks of which there are three species in North America.

In the southeastern parts of the United States, most of us have the chance to see at least two of the three accipiter species found in North America—the common and widespread Sharp-shinned and Cooper’s Hawks.  The larger Northern Goshawk strays only rarely into Mississippi.  It is typically an elusive bird of dense, mostly coniferous northern woods.  The unique plumage that the adult goshawk has makes it unlikely to be confused with its more common cousins.  However, the two smaller hawks are very similar in appearance.

In fact, these agile little hawks can look so frustratingly alike, especially in flight, that in making a call oftentimes the bewildered birder can only be certain that he/she has seen an accipiter.  An estimate of the bird’s size isn’t always of much help, either, because of the near overlap in the range of body lengths of Sharp-shinned and Cooper’s Hawks.  There is, of course, the difference between the species’ long tails: the Cooper’s Hawk’s is rounded; the Sharp-shinned’s is squared.  Sometimes this feature isn’t very noticeable or obvious, though, and that’s when knowing the differences in body shape between the two birds comes in handy.

Perched, a Sharp-shinned Hawk usually sits in a more upright position than the Cooper’s.  Its chest is proportionately wider and its hips narrower than its larger relatives.  It’s almost as if the little “Sharpie” has to make up for its diminutive size by adopting this straight, proud posture.  Another way you can tell the smaller species from the larger is by noting the leg thickness.  Sharp-shinned Hawks have very thin legs, a trait noticeable in even the large female birds that resemble Cooper’s Hawks.  Head patterning is a little different, too; the Sharp-shinned has a more extensive black cap than the Cooper’s, and on a brownish-colored immature bird the presence of a reddish cast to the head feathers indicates Cooper’s.

The proportionately long neck of the Cooper's Hawk is a useful feature in separating the species from the Sharp-shinned, especially when the birds are in flight.  Flight pattern can also be used as an identification tool, and the more experience you have with observing flying accipiters, the easier it becomes to distinguish the two species.  The Sharp-shinned Hawk has faster, more erratic wingbeats when compared to the Cooper’s Hawk, whose wingbeats are easier to count.

In my experience, it certainly isn’t easy to count feeding songbirds when a hawk decides to show up and check out the menu!  But then I guess we’d be ready to leave, too, if we  were those birds—or for that matter, if we were lizards, frogs, mice, rats, or insects.  All of these creatures are consumed by Sharp-shinned and Cooper’s Hawks, although to a lesser degree than birds.

Both the Sharp-shinned and Cooper’s Hawks declined perilously in numbers from DDT poisoning after World War II and were seen infrequently in Mississippi.  After the ban on DDT in 1972, their numbers steadily increased, and now they can be found commonly in the fall, winter and spring.  Cooper’s Hawks used to be fairly numerous and widespread as breeding residents in the state, but they are now scarce nesters in the summer months.

Part of the supposed scarcity could be from the fact that the hawks’ nests are tricky to find.  In mixed forest where the Cooper’s Hawk nests, it’s difficult to see through all the leaves that conceal the tree branches.  If you were to discover a Cooper’s Hawk’s nest, it would be a platform of sticks and twigs on a branch near the trunk of a deciduous tree.  The male hawk constructs the nest with some help from the female.  The brown-spotted eggs are incubated for 32-36 days, mostly by the female.  The resulting young hawks can fly after 27-34 days but are still dependent on their parents for over a month after that.

I said that the Cooper’s Hawks build their own nests, but there are always exceptions in the avian world.  Occasionally, these hawks will take the easy road and use an old crow’s nest.  Stranger still, a few nests have even been built on the ground.

I hope this article will help you appreciate the Sharp-shinned and Cooper’s Hawks even more, whether you see them darting through a dense forest, gliding high over fields or even stealthily hunting near your backyard feeders.  Just be very thankful that you’re not a little songbird!

Sources:

Birds of Mississippi.  Turcotte, William H., and Watts, David L.  University Press of Mississippi, Jackson.  Mississippi Department of Wildlife, Fisheries and Parks.  1999.

The Cornell Lab of Ornithology’s Guide to Birds of North America, version 3.  2001.

Field Guide to the Birds of North America, Third Edition.  National Geographic Society, 1145 17th Street N.W., Washington, DC.  1999.

Hawks, Owls, and Wildlife.  Craighead, John J., and Craighead, Frank C.  Wildlife Management Institute.  1956.