CBC Data & Bird Trends

Summaries of some bird trends we see from CBC data - prior to the 100th count.

Continentally, several trends stand out within the 98th CBC. There was a significant number of Pacific or Arctic/Pacific loons reported in eastern North America during this season. Several factors could be responsible for this, with the most obvious perhaps being the weather effects already discussed. However, winter-plumaged loons can be quite difficult to identify. As the considerable pool of observers on Christmas Bird Counts becomes better tuned to the nuances of basic-plumaged loons, it could be that the smattering of Pacific Loons wintering along the Atlantic coast of North America are finally being picked out from runt Common Loons, or distantly-viewed Red-throateds. A new identification challenge is already on the horizon for this taxon; separation of winter Pacific Loons from their Asiatic cousins, the Arctic Loon. Life is never simple in the world of birdwatching.

Broad-winged Hawk
Another species being reported and accepted with increasing frequency on Christmas Bird Counts is Broad-winged Hawk. This species should not be in North America during the winter season at all, with the notable exception of the southern tip of Florida and the Keys. ID questions quickly arise when immature-plumaged Broad-wingeds are reported in winter; the very similar appearing Red-shouldered Hawk is far more likely, and immature birds in molt can be an especially difficult identification challenge. However, some of the birds being reported are adult Broad-wingeds, and particularly in odd seasons like the one leading to the 98th Count reports of this species on counts must be carefully evaluated.

Trumpeter Swan
Trumpeter Swans present an increasing challenge to participants on CBCs. Trumpeters until recently were restricted to their well-known western haunts, but this species is now being reintroduced to its former range in the midwest and east. Introduced Trumpeters are showing up along the Mississippi, as well as in eastern Canada and along the mid-Atlantic seaboard. Several of these introductions appear to be taking hold quite well, and CBC data are being used to evaluate the status of this species in central and eastern North America. As of yet Trumpeter Swan is only a "countable" species in the west, but very soon it may be established again in other regions, giving counters three species of swans to haggle over. In fact, a fourth species, Whooper Swan, may become established in North America as well -- check out the Newburyport, Massachusetts count!

House Finch and Eurasian Collared-Dove
Many studies have been conducted using Christmas Bird Count data tracking the spread of the House Finch across eastern North America since its introduction into the greater New York City area in the mid-1940s. A similar study crying to be undertaken is the documentation of the spread of Eurasian Collared-Dove from the southeast across the continent. This introduced species is being encountered in larger numbers in the southeast every year, and is extending its range rapidly both northward and westward. In the 98th Count they were noted as up in numbers in Georgia/Florida, Alabama/Mississippi, first record in Arkansas, way up in numbers in Louisiana, and increasing in Texas. Much of North America may soon have another dove competing with Mourning Doves at feeders.

American Kestrel and Northern Bobwhite
Two species reported upon for the past several years in this summary and throughout the Regional Summaries as universally in decline are American Kestrel and Northern Bobwhite. These two species again were reported throughout North America as in low or record low numbers. The long-term analysis of Christmas Bird Count data, well beyond that in the scope of this annual summary, should be undertaken to document the extent of these apparent declines. The status of Northern Bobwhite is especially open to question, as local releases of birds as a game species may tend to cloud the issue of the status of resident populations. Along this line, please note Dave Sonneborn’s comments from Alaska! The Christmas Bird Count may also be tracking the disappearance of one species from the United States; Smooth-billed Ani. This species’ stronghold has been south Florida, but Paul Sykes warns it may be on the way out, for reasons not understood. As illustrated in Paul’s summary, CBC data dramatically document the decline of this species, and may be used to highlight species that should be of management concern.

Grasshopper Sparrow
For the past eleven years we have tracked species of interest in the Christmas Bird Count in this summary. The table  once again lists these species, starting with our diminutive skulker, the Grasshopper Sparrow. The number of birds reported this season was mid-way between sightings in the 96th and 97th Counts; fewer individuals were identified than last season, but in more count circles and in more regions. This makes sense given the weather pattern; more birds were probably dispersed farther north, and the species may have been less concentrated on its North American wintering grounds. A species like Grasshopper Sparrow poses a continual enigma to researchers utilizing data such as Christmas Bird Counts; although presenting occasional identification questions, and not the easiest bird to locate outside the breeding season, it is a species of interest to many field observers, and it is common enough to be encountered with some frequency. The historical CBC data now becoming available through BirdSource will shed even better light on the long-term status of Grasshopper Sparrow than can be achieved in the year-to-year comparisons included here.

Bohemian Waxwing
In this forum we do better with a species such as Bohemian Waxwing, our next suspect in table . There was a significant movement of this species during the 98th Count, though it did not follow the same pattern as the winter finch flight. Bohemian Waxwings were noted in unusually low numbers in their core range in Alaska and the interior of western Canada, but were in high numbers in eastern Canada, with large flocks appearing all the way to the Atlantic Coast in the Canadian Maritimes. There was a fair flight into northern New England, but with a sharp southern cut-off that restricted the flight to a much smaller region than that seen in the epic flight of the winter of the 94th Count. Areas in the northern Rockies also well-clad with large flocks of Bohemian Waxwings, but very few made it south of Wyoming. Overall there was a major, but well-defined movement away from the expected breeding areas of northwestern North America, producing large numbers of these wandering frugivores in some regions, but not to the extent of four years ago. Winter irruptive species are very well tracked by the Christmas Bird Count; observers are out in force over the entire continent, and breadth and scope of these annual movements can be compared and contrasted over time utilizing the data collected.

Evening Grosbeak
The remaining three species in table, Evening Grosbeak, Red Crossbill, and Common Redpoll, illustrate the varying ways that species respond during superflight years. Evening Grosbeaks moved early in the flight, and in fact during the Christmas Bird Count period were tallied in only average numbers. Several areas, mostly in the midwest or central Rockies, experienced a paucity of these voracious feeder birds. The only region with even fair numbers of Evening Grosbeaks reported was northeastern North America, but even these totals were far below those of large flight year like the 94th and 96th Counts. Where did they go? Perhaps Evening Grosbeaks move southward in concentrated fashion during the fall, then dispersed into smaller flocks for the winter, resulting in fewer total birds tallied per count.

Red Crossbills
Red Crossbills, when encountered, are seldom found in flocks approaching the size of Evening Grosbeak herds (table). Over much of North America it is a treat to encounter this species at all on a Christmas Bird Count. Therefore the total of 242 counts in 50 regions encountering a total of over 5500 Red Crossbills is notable, especially when we realize that this was just the tip of the iceberg. Crossbill numbers (both Reds and White-wingeds) built throughout the winter, with some birds dispersing well into the southern lowland regions of North America, only retreating northward after the end of February. Interestingly, there were very few Red Crossbills reported this season in the region where they did undertake a major irruption during the 97th Count, in the southern Rockies and the desert southwest. Perhaps they knew to emigrate to greener pastures. However, clouding the Red Crossbill picture is a taxonomic enigma: what we currently identify as "Red Crossbill" may well be several closely-related species, separable in the field only by bill size and call notes. The "Type 2" Red Crossbills, the breeders in the southern Rockies and desert southwest sky islands, probably were not involved in this year’s superflight.

Common Redpoll
Then there were the redpolls (table). Much of the continent was covered by a chipping swarm of Common Redpolls during the winter season of 1997-1998, and they were well documented in the 98th Count. Common Redpoll was noted as being in high or record numbers in the Canadian Maritimes, Quebec/Ontario, New England, New York, Ohio, Wisconsin, Illinois, Iowa, the Dakotas, and Montana/Idaho. Over 40,000 were found in Ontario alone, and they were only missed on one count in that province. A flock even made its way to Bermuda! Overall, about one-third of all North American counts encountered Common Redpolls, in numbers approaching the epic flight of the 94th Count. It is interesting to note that some sort of irruption of Common Redpolls happens roughly every other year; we’ll see what happens in the 100th Count.