Friday, November 14, 2008

Christmas Bird Counts of Berrien County: 1961-2007

With the Christmas Season looming on the horizon (yes, it’s true) I thought it would be fun, and hopefully instructional, to provide a quick overview of Christmas Bird Counts (CBCs) in Berrien County. So here goes . . .

Caption: European Starling (Sturnus vulgaris), the most abundant species recorded on Berrien County CBCs. Image is from the Introduced Species Summary Project at Columbia University.
The history of the CBC in Berrien County spans a 47-year period, 1961-2007. Over those 47 years, 157 counts were conducted at 4 locations: Berrien Springs (47 counts: 1961-2007), Coloma (36: 1972-2007), New Buffalo (29: 1969-1975 & 1986-2007), and Niles (45: 1961-1978 & 1981-2007). That effort resulted in 10,588 encounters (i.e., an encounter entails the detection of one species, regardless of the number of individuals, on one CBC) with 1,539,691 individuals of a nominal 183 species; on average, that equates to 9,807 inviduals of 67 species/count/year. One hundred fifty-nine species were recorded at Berrien Springs, 139 at New Buffalo, and 131 each at Coloma and Niles.

Evenness of Distribution: One hundred and twelve species (61 percent) were recorded at all four CBC sites, 17 (9 percent) at three, 17 at two, and 36 (20 percent) at just one.

Yearly Regularity: Thirty-three species (18 percent) were recorded in each of the 47 years, 27 (15 percent) in just one year; the median regularity was 22 years, or 47 percent.

Frequency of Occurrence: Fourteen species (8 percent) were recorded on all 157 counts, 27 (15 percent) on just one count; the median frequency was 32 counts, or 20 percent.

The Big Twelve: The following species are ranked in decreasing order of abundance based on a combination of three criteria: (a) total number recorded; (b) mean count when detected, and (c) median count when detected. The values for each of these criteria are presented as percentages relative to the highest-ranking species in each category (European Starling;i.e., the median count for Northern Cardinal was 9.2 percent that of the starling). Ranks (overall and for individual critera) are in curly brackets. Each of the species listed below ranked in the top 10 in at least one of the three abundance criteria:
  • European Starling {1} — (a) 100{1} [n=372,201] — (b) 100{1} [Mean=2,373.9] — (c) 100{1} [Median=1,213]
  • House Sparrow {2}: (a) 47.2{2} — (b) 47.2{2} — (c) 75.0{2}
  • Dark-eyed Junco {3}: (a) 32.2{3} — (b) 32.2{3} - (c) 53.5{3}
  • American Tree Sparrow {4}: (a) 16.5{6} — (b) 16.5{7} — (c) 28.2{4}
  • Canada Goose {6}: (a) 16.0{8} — (b) 20.4{5} — (c) 24.8{5}
  • Ring-billed Gull {7}: (a) 21.2{4} — (b) 23.4{4} — (c) 15.1{13}
  • Mallard {7.7}: (a) 16.3{7} — (b) 16.3{8} — (c) 24.0{8}
  • Herring Gull {8.7}: (a) 16.8{5} — (b) 17.2{6} — (c) 13.5{15}
  • Mourning Dove {8.7}: (a) 14.3{9} — (b) 14.4{10} — (c) 24.2{7}
  • House Finch {10.3}: (a) 8.5{13} — (b) 13.8{12} — (c) 24.4{6}
  • Rock Pigeon {10.3}: (a) 12.7{11} — (b) 15.6{9} — (c) 15.5{11}
  • American Crow {10}: (a) 13.8{10} — (b) 13.8{11} — (c) 20.1{9}
  • Northern Cardinal {11.7}: (a) 9.2{12} — (b) 9.2{13} — (c) 17.4{10}
  • Notable High Counts: Of the 94 species detected 30 or more times, 10 had high counts that exceeded the median by a factor of 50 or more. Information provided for each species includes the high count (the site and year of the high count); and the factor by which the high count exceeded the median:
  • Common Merganser 1,224 (Berrien Springs, 1972); 84x
  • Red-breasted Merganser: 1,524 (Berrien Springs, 2003); 254x
  • Ring-necked Pheasant: 429 (Berrien Springs, 1973); 54x
  • American Coot: 2,175 (Coloma, 1994); 272x
  • American Robin: 1,366 (Berrien Springs, 2004); 137x
  • Red-winged Blackbird: 235 (New Buffalo 2001); 59x
  • Common Grackle: 3,120 (Berrien Springs, 1984); 1,040x
  • Brown-headed Cowbird: 818 (Berrien Springs, 1982); 136x
  • Lapland Longspur: 4,141 (New Buffalo, 1973); 1,035x
  • Common Redpoll: 1,300 (Berrien Springs, 1969); 52x
  • Acknowledgment: This overview was compiled with the aid of the CBC database.

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