Summary of the Fort Belvoir CBC, 30 Dec 2001 (Sorry its a bit late)
The Fort Belvoir CBC took place December 30, 2001; this was the 58th year
that this circle was counted. The temperature range was 21-34 F with clear
skies, significant winds were noted in the morning (20-30 mph) becoming
calmer in the afternoon (0-10 mph). Bodies of still water were partly frozen
and moving water was open. A total of 113 species were recorded in the
count, about 6% below the 10-year numerical average. The circle had 170
counters in the field in 59-62 parties and there were 2 feeder watchers. The
following summary is based upon data that will be submitted to National
Audubon and is subject to change by reviewing authorities.
A total of 15 high-count records were set and 3 high-count records were tied.
There was one new species added to the historical database for this circle:
selasphorus hummingbird species (175 species have now been recorded in this
circle). In addition, four unusual species were noted: Great Egret (4th
occurrence in 20 years), Black Scoter (4th), Rough-legged Hawk (2nd, last
seen 1981), and Peregrine Falcon (2nd). Species found that occurred 10 or
less times in the last 20 years were: Wild Turkey (8th), Greater Yellowlegs
(8th), Laughing Gull (10th), Lesser Black-backed Gull (10th), Barn Owl
(10th), Chipping Sparrow (9th). There were two count week (CW) species,
Merlin and Baltimore Oriole.
Generally speaking, the count was relatively surprising given the paucity of
rare or out-of-season species. Warm weather species were up in numbers and
some were near or exceeded previous historic highs. Cold weather species
were down and one, Red-breasted Merganser (one counted) had its worst showing
since 1976 (when none were recorded). It is interesting to point out that
several species were down significantly as compared to last year's count
(remember the freezing weather?) when the effects of cold temperatures tended
to concentrate numbers. For instance; Canada Goose, both scaup species,
Common Merganser, Red-breasted Merganser, and Bald Eagle had extremely high
numbers last year that exceeded this year's count.
As an aid to better understand the long-term trends in this circle's count
data, I have recently begun a database of the count that weights the species
totals by Party Hours. I have used the data for the last 10 count years to
determine averages and standard deviation from the average. This approach
assumes a Gaussian distribution of a limited data set and so derived standard
deviations may only be reasonable for year round species whose numbers do not
fluctuate greatly. Hence, this assumption is likely crude for species whose
winter numbers greatly fluctuate or are small in magnitude.
The following species had weighted counts that exceeded the 10 year average
by 3 or more standard deviations (for a Gaussian distribution occurrences
outside 3 standard deviations take place less than 1 time out of a hundred).
Note that many of these species exhibited historical high counts.
Double-crested Cormorant (HC)
Wood Duck (HC)
Canvasback (numbers can fluctuate greatly)
Ruddy Duck (HC, numbers can fluctuate greatly)
Wild Turkey (HC)
American Robin (numbers can fluctuate greatly)
Fox Sparrow (HC)
White-crowned Sparrow (HC tie, a change in count strategy has likely resulted
in this effect)
The following species had weighted counts that exceeded the 10 year average
by 2 -3 standard deviations:
Greater Yellowlegs (HC, numbers can fluctuate markedly)
Song Sparrow (HC)
Just as some species have increased wintering numbers, others can have
decreased numbers. The following species had weighted counts that fell short
of the 10-year averages by 3 or more standard deviations:
Hairy Woodpecker
The following species had weighted counts that fell short of the 10-year
averages by 2 - 3 standard deviations:
Northern Flicker (numbers can fluctuate markedly)
At the end of count day several observers had noted to me that the total
count of birds seemed to be less than in previous years. In support of this
statement, the database indicates that several of the more common species
exhibited counts that were between 1 and 2 standard deviations below 10-year
averages. These were:
Great Blue Heron, Red-breasted Merganser (only one noted), Red-shouldered
Hawk, American Kestrel, Great Black-backed Gull, Rock Dove, Mourning Dove,
Belted Kingfisher, Pileated Woodpecker, Blue Jay, Carolina Wren, E. Starling,
Yellow-rumped Warbler, House Finch, and House Sparrow.
The decrease in the counts of these, and of some of the other species listed
above, may have been effected by the strong winds present during the morning
of the count.
Based upon historical records, the following species that were not recorded
may have been missed: Long-tailed Duck (recorded in 18 out of 20 years),
American Woodcock (20), House Wren (17), and American Pipit (18). King Rail,
also not recorded this year, had been observed 12 times and one count week in
the last 20 years.
Lastly, I am pleased to note that Brown Creeper weighted counts were very
close to the 10-year average, and thus countering a 6-year decreasing trend.
The following are the totals for the count.
Common Loon 1
Pied-billed Grebe 31
Horned Grebe 3
Double-crested Cormorant 79 HC
Great Blue Heron 223
Great Egret 1 US
Black Vulture 75
Turkey Vulture 126
Canada Goose 10,189
Tundra Swan 1,069
Mute Swan 6 HC tie
Wood Duck 174 HC
Gadwall 466
American Wigeon 83
American Black Duck 1,696
Mallard 3,869
Northern Shoveler 28
Northern Pintail 179
American Green-winged Teal 355
Canvasback 4,623
Redhead 47
Ring-necked Duck 467
Greater Scaup 4
Lesser Scaup 5,192
scaup sp. 6,143
Black Scoter 1 US
Surf Scoter 1
Common Goldeneye 6
Bufflehead 732
Hooded Merganser 236
Common Merganser 389
Red-breasted Merganser 1
Ruddy Duck 14,095 HC
Bald Eagle 118, 76 adult, 42 immature
Northern Harrier 4
Sharp-shinned Hawk 29 HC
Cooper's Hawk 6
accipiter sp. 2
Red-shouldered Hawk 40
Red-tailed Hawk 82
Rough-legged Hawk 1 US
American Kestrel 6
Merlin CW
Peregrine Falcon 2 US, HC tie
Wild Turkey 21 HC
Northern Bobwhite 8
American Coot 898
Killdeer 158
Greater Yellowlegs 22 HC
Common Snipe 28
Laughing Gull 1
Bonaparte's Gull 7
Ring-billed Gull 6,718
Herring Gull 953
Lesser Black-backed Gull 1
Greater Black-backed Gull 118
gull sp. 334
Rock Dove 195
Mourning Dove 1,053
Barn Owl 1
Eastern Screech Owl 12
Great Horned Owl 12
Barred Owl 18
selasphorus hmmingbird sp. 1 US
Belted Kingfisher 51
Red-headed Woodpecker 2
Red-bellied Woodpecker 464
Yellow-bellied Sapsucker 68
Downy Woodpecker 396 HC
Hairy Woodpecker 56
Northern Flicker 331
Pileated Woodpecker 86
Eastern Phoebe 19 HC
Blue Jay 382
American Crow 2,931
Fish Crow 366
crow sp. 2,775
Carolina Chickadee 1,728 HC
Tufted Titmouse 1,198 HC
Red-breasted Nuthatch 8
White-breasted Nuthatch 383 HC
Brown Creeper 71
Carolina Wren 542
Winter Wren 38
Golden-crowned Kinglet 230
Ruby-crowned Kinglet 95
Eastern Bluebird 629 HC
Hermit Thrush 125
American Robin 1,665
Gray Catbird 1
Northern Mockingbird 239
Brown Thrasher 4
Cedar Waxwing 542
European Starling 3,370
Yellow-rumped (Myrtle) Warbler 117
Pine Warbler 1
Eastern Towhee 60
American Tree Sparrow 11
Chipping Sparrow 2
Field Sparrow 134
Savannah Sparrow 1
Fox Sparrow 41 HC
Song Sparrow 1,513 HC
Swamp Sparrow 190
White-throated Sparrow 1,736
White-crowned Sparrow 23 HC tie
Dark-eyed Junco 2,137
Northern Cardinal 1,101 HC
Red-winged Blackbird 1,512
Eastern Meadowlark 4
Rusty Blackbird 35
Common Grackle 1,096
Brown-headed Cowbird 232
blackbird sp. 44
Baltimore Oriole CW
Purple Finch 9
House Finch 526
Pine Siskin 1
American Goldfinch 805
House Sparrow 490
Total Birds: 89,236
For those desiring additional information, please write me.
Kurt Gaskill, compiler Fort Belvoir CBC
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