THE CONNECTICUT WARBLER A Journal of Connecticut Ornithology Volume 34 No. 1 January 2014 Pages 1-28 The Connecticut Warbler A Journal of Connecticut Ornithology Volume 34, Number 1 January 2014 CONTENTS 1 Short-Range Migratory Strategies Joseph Belanger 10 Notes on Behavior, Status and Distribution Paul Carrier 14 Connecticut Field Notes Greg Hanisek 25 A Picture Is Worth A Thousand Birds Mark Szantyr 28 Photo Challenge ON THE COVER Paul Carrier bases his bird illustrations on close observa- tion, and in this issue he offers two notes on bird behav- ior around his home in Harwinton. His cover art illus- trates typical ground-feeding species , a White-throated Sparrow and a Dark-eyed Junco, feeding on tree seeds, the subject of one of the notes. SHORT-RANGE MIGRATORY STRATEGIES By Joseph Belanger Introduction After a summer of predictable breeding behavior, migra- tory demands across the northeastern United States scatter many species southward across the continent and beyond. But a number of short-range migrants always seem to leave some individuals behind, occasionally in substantial num- bers. The exact reason for this has always been obscure, and often dismissed as the whimsy of local populations. But when Christmas and summer bird count data is subjected to Shannon-Wiener analysis, another strategy emerges. Winter rhythms across this region follow a distinctive pattern, with many short-range migrants apparently seeking to minimize their migration distance each year. Selected Count Circles For the purposes of this review, six Christmas count circles and three summer counts (held annually in June) were se- lected from the northeast, and these count circles are listed within Table 1. Christmas count data was readily available on the internet, and was downloaded for the years 2007 - 2011 (BirdSource, CBC data). Summer counts were gathered from internet sources (Willow Beach Field Naturalist, SBC data) and from published material (Zeranski and Comins 2007 - 2011). This count data was analyzed using the Shannon-Wiener In- dex (Shannon 1948), based upon the underlying biodiversity theory that a well-balanced ecosystem is an equally propor- tioned one (Heywood 1995). For such systems all species are numerically well-represented, and are therefore capable of losing numerous individuals before they suffer any material weakening. Conversely, an ecosystem characterized by a handful of dominant species and several marginal popula- tions is subject to sudden disruption. The Connecticut Warbler, Vol. 34 No 1, January 2014 1 2 BELANGER The Shannon-Wiener Index (H) measures biodiversity, and has two components. The first increases with the number of species, while the second (evenness) reflects the proportional- ity of these species (Table 2). The Evenness Index (E) breaks out the proportional com- ponent of Shannon-Wiener, and generates an index of 1.0 (100%) for perfect proportionality. As such, this index gen- erates data that resembles test scores, and these scores com- prise the central focus of this paper. (H) = -sum [P(i) x Ln P(i)] x(i) = # of each species N = # of total birds (E) = H/Ln S P(i) = x(i)/N Ln = natural log S = # of species The Greater White-fronted Goose (Anser albifrons) on the left and the Great Black-backed Gull (Larus marinus) on the right represent opposite ends of the migration spectrum. This goose is a long distance migrant that probably bred in Greenland, while the gull is a year-round resident species in the northeast. Both birds were digi-scoped on Silver Lake in Westchester County, New York, during the winter of 2009-2010. While both species are absent from this pond in summer, they are fairly regular visitors to this location during winter. These two species represent the variable and disparate sources that contribute to the avian population of a geographic area each winter. SHORT-RANGE MIGRATORY STRATEGIES 3 Shannon-Wiener Biodiversity Index Transitional - Northern Hardwood Forest 0.9 0.8 ex 0.7 d n I 0.6 ess 0.5 n 0.4 en v E 0.3 0.2 0.1 0 2007 2008 2009 2010 2011 Barkhamsted Summer Barkhamsted Christmas Peterborough Christmas Graph 1 - The mixed transitional - northern hardwood forest demonstrates a high level of summer breeding stability, and despite a sharp drop-off in the number of species, a surprisingly stable evenness index during Christmas counts. Shannon-Wiener Biodiversity Index Coastal Christmas Counts 0.8 0.7 ex 0.6 d n I 0.5 ess 0.4 n en v 0.3 E 0.2 0.1 0 2007 2008 2009 2010 2011 Cape May Christmas Nantucket Christmas Graph 2 - Coastal areas feature pronounced volatility in Christmas count results, reflecting the reliance upon these areas as refuges for many stressed or vagrant migrants. The Connecticut Warbler, Vol. 34 No 1, January 2014 4 BELANGER Table 1 - Selected Count Circles Count Geographic Ecological Circle Location Province Barkhamsted, Interior- Transitional Forest - CT New England Northern Hardwood Peterborough- Interior- Transitional Forest - Hancock, NH New England Northern Hardwood Greenwich- Coastal- Eastern Broadleaf Forest Stamford, CT Sound Northumberland/ Interior- Eastern Broadleaf Forest Port Hope-Cobourg, ON Great Lakes Cape May, Coastal- Eastern Broadleaf Forest NJ Peninsula Pine Barrens subregion Nantucket, Coastal- Eastern Broadleaf Forest MA Island Pine Barrens subregion Table 2 - Count Data Summer Counts Christmas Counts 2007 2008 2009 2010 2011 2007 2008 2009 2010 2011 Barkhamsted, CT # Species 120 120 126 128 123 74 71 65 67 66 Shannon-Wiener 4.05 4.04 4.07 4.06 4.04 3.25 3.07 3.10 3.07 3.11 Evenness 0.85 0.84 0.84 0.84 0.84 0.76 0.72 0.74 0.73 0.74 Peterborough-Hancock, NH # Species -- -- -- -- -- 41 40 44 47 54 Shannon-Wiener -- -- -- -- -- 2.83 2.58 2.80 2.79 2.96 Evenness -- -- -- -- -- 0.76 0.70 0.74 0.72 0.74 Greenwich-Stamford, CT # Species 140 148 141 133 132 123 118 116 108 103 Shannon-Wiener 3.84 3.83 3.84 3.74 3.75 3.35 3.44 3.05 3.46 3.37 Evenness 0.78 0.77 0.78 0.76 0.77 0.70 0.72 0.64 0.74 0.73 Northumberland/Port Hope # Species 143 140 140 138 136 83 81 72 77 77 Shannon-Wiener 3.82 3.88 3.85 3.69 3.81 3.15 2.99 2.87 2.98 2.69 Evenness 0.77 0.79 0.78 0.75 0.78 0.71 0.68 0.67 0.69 0.62 Cape May, NJ # Species -- -- -- -- -- 161 155 150 152 152 Shannon-Wiener -- -- -- -- -- 3.62 3.42 3.32 3.59 2.88 Evenness -- -- -- -- -- 0.71 0.68 0.66 0.71 0.57 Nantucket, MA # Species -- -- -- -- -- 129 134 118 128 134 Shannon-Wiener -- -- -- -- -- 2.13 2.22 3.35 3.25 2.18 Evenness -- -- -- -- -- 0.44 0.45 0.70 0.67 0.44 SHORT-RANGE MIGRATORY STRATEGIES 5 Transitional - Northern Hardwood Forest Barkhamsted (Connecticut) and Peterborough-Hancock (New Hampshire) comprise two count circles that are found within the mixed transitional - northern hardwood forest, a region characterized by beech, birch, maple, pine and hemlock (McNab and Avers 1994). This region forms a transitional zone between the North American temperate hardwoods and the spruce-fir biome to the north. As such, it demonstrates some characteristic traits of the boreal biome, with a high reproduction capacity and a sudden drop in win- ter diversity. Summer data from the Barkhamsted count generates a very high Shannon-Wiener biodiversity index, much of which is driven by a strong evenness component. In fact, while the Barkhamsted summer circle did not exhibit a particularly high species count, its 84% evenness index was the highest in this review (Table 2). In addition, while this region’s Christ- mas count results showed a dramatic drop in the number of species, Christmas data also generated surprisingly stable results. Both the Barkhamsted and Peterborough-Hancock counts featured an evenness index that consistently hovered roughly 10% below that of the Barkhamsted summer data (Graph 1). A review of the Peterborough-Hancock Christmas bird count helps to explain this region’s stability during the winter months. In 2009 this Christmas count recorded 605 Blue Jays and 20 American Robins, but the same count reversed these results in 2011 with 208 Blue Jays and 795 American Robins. Since these two species are not generally regarded as direct competitors, it seems likely that prevailing weather condi- tions and snow cover closed some ecological niches while opening others, acting liking a conveyor belt across the entire region. Eastern Broadleaf Forest Greenwich-Stamford (Connecticut) and Port Hope-Cobourg/ Northumberland (Ontario) represent count circles that are The Connecticut Warbler, Vol. 34 No 1, January 2014 6 BELANGER located within the eastern broadleaf forest, an area primar- ily dominated by oak and hickory (McNab and Avers 1994). Greenwich-Stamford and Northumberland have conducted regular summer counts for many years, providing important summer data for this region. The Northumberland summer bird count data is roughly analogous to the Port Hope-Co- bourg Christmas count, and while these circles are not per- fectly aligned, they constitute very similar overlapping areas. Both circles are located on Lake Ontario, approximately 75 miles east of Toronto. The eastern broadleaf region generated data results that broadly resembled the previous forest zone, but with less dramatic changes between summer and winter. Summer count evenness averaged 77% for both counts, dropping roughly 6% in Connecticut and 10% in Ontario during Christ- mas counts. And while both count circles featured Christmas data that was less stable than those of the previous forest region, they continued to demonstrate a distinctly defin- able pattern that seems to characterize inland sites (Table 2).