The 117th CBC in Louisiana

During the 2016-2017 (117^th) Audubon Christmas Bird Count, 222 parties (16 more than last year) dedicated 1722 party-hours (95 more than last year) across 29 counts (2 more than last year). Great to see the Louisiana CBC efforts continue to increase! One new CBC was added to the docket, Palmetto Island CBC, and one count was resurrected, Tensas N.W.R. CBC, not having been run since the 112^th CBC. Thank you to those and compilers that coordinated the count effort this year, as well as all the volunteer counters!

The species total across all Louisiana CBCs was 259 species, one shy of last year. Additional “non-countable” species that are locally established included Canada Goose, Muscovy Duck, Whooping Crane (an experimentally reintroduced population), and Monk Parakeet. A total of 7,271,184 birds were counted with Red-winged Blackbird (4,216,692), Brown-headed Cowbird (2,044,020), and Snow Goose (281,773) being the most numerous.

Among the 29 Louisiana CBCs, 24 of them topped 100 species, and four topped 150 species: Palmetto Island (156), New Orleans (154), Sabine (151), and Creole (150). Although the top counts this year were short of last year’s two top counts, which reached 161 and 160 species, it is exciting to see a new CBC (Palmetto Island) and a southeastern Louisiana count (New Orleans) with such high counts. In north Louisiana, the counts with the most species were Pine Prairie (113) and Natchitoches (112).

It was a good year for winter hold-over warblers, with 16 species represented. The most remarkable perhaps were Magnolia Warbler (2; Grand Isle, Venice) and Black-throated Blue Warbler (1; Thibodaux). Other species outside of the six common species included Black-and-white Warbler (9 among 7 counts), Prairie Warbler (6 among 5 counts), Nashville Warbler (3; Creole, Grand Isle, Sabine N.W.R.), American Redstart (3; Grand Isle, New Orleans, Venice), Northern Waterthrush (2; White Lake, Venice), Yellow Warbler (2; Venice), Yellow-throated Warbler (2; Venice), and Black-throated Green Warbler (1; New Orleans).

Other rarities of note included Fulvous Whistling-Duck (17; Creole), a stake-out Tundra Swan (1; Sweet-Lake-Cameron Prairie N.W.R.), good counts of both Surf Scoter (10) and Black Scoter (65) from the Sabine N.W.R. CBC, Long-tailed Duck (1; Sabine N.W.R.), Magnificent Frigatebird (2; Grand Isle, Venice), a stake-out Brown Booby (St. Tammany), Broad-winged Hawk (1; Grand Isle), Swainson’s Hawk (1; Creole), Purple Gallinule (2; Sweet-Lake-Cameron Prairie N.W.R., St. Tammany), Groove-billed Ani (1; Grand Isle), Lesser Nighthawk (1; Venice), Allen’s Hummingbird (1; Reserve-Bonnet Carre Spillway), Broad-billed Hummingbird (3; Reserve-Bonnet Carre Spillway, St. Tammany), Brown-crested Flycatcher (2; New Orleans), Couch’s Kingbird (1; St. Tammany), Bell’s Vireo (2; Johnson’s Bayou, Sabine N.W.R.), Barn Swallow (2; Palmetto Island), Cave Swallow (18; Lacassine N.W.R.-Thornwell, Sweet Lake-Cameron Prairie N.W.R.), Clay-colored Sparrow (1; Creole), Harris’s Sparrow (1; New Orleans), Western Tanager (1; Northshore-Slidell), and Orchard Oriole (1; New Orleans).

It is always interesting to see how each winter plays out in terms of representation by our more regularly occurring species. This was a disappointingly poor year especially for sparrows, as well as several other short-distance migrants. Corrected for party-hours, White-throated Sparrow and Swamp Sparrow numbers hit a new record low, both breaking last-year’s record lows, and continuing -3.6%/year and -2.7%/year declines, respectively, since 1970. Figure 1 shows these declines as calculated using a hierarchical Bayesian approach, borrowed from Soykan et al. (2016, Ecosphere 7: e01351).

Even some common species, like Carolina Chickadee and Northern Cardinal, appear to be experiencing long-term declines, at -0.4%/year and -1.2%/year, respectively (Figure 2).

This was a relatively decent invasion year for Purple Finch, at least in modern history, but nothing like the invasion years of the 1970s and 1980s (Figure 3).

On the other hand, some species are showing long-term increases, like Eastern Phoebe and Eastern Bluebird, which are increasing at +1.9%/year and +3.6%/year, respectively (Figure 4). In addition, the continuing increase and establishment of once south-Texas species, like Black-bellied Whistling-Duck (5140 from 8 CBCs) and Crested Caracara (100 from 10 CBCs) are evident.

Participation in the Christmas Bird Count provides long-term perspectives on how North American bird communities continue to shift and change. Thanks to all the compilers who ensure this legacy continues and to all the volunteers that spend their holiday season with the birds. Here’s looking forward to next year!