2015 Bird Breeding Season summary

Least Tern with Chick
photo by Vince Thomas

The final report of the breeding bird species at Bolsa Chica for 2015 is in thanks to CA Dept. of Fish and Wildlife’s Kelly O’Reilly.  Many other species breed at Bolsa Chica, but these four are the main species that the CA Dept. of Fish and Wildlife monitor on an annual basis.  Thanks for the report Kelly!

CDFW Bolsa Chica Ecological Reserve Breeding Season Results, 2015

Belding Savannah sparrow, Passerculus sandwichensis beldingi

Surveys conducted in March resulted in 345 breeding territories on the entire reserve.

California least tern, Sternula antillarum browni

Overall, 204 nests were initiated at Bolsa Chica during 2015. Only two of five nesting colonies were successful: South Tern Island [64 nests; 112 eggs; 78 chicks (4 dead chicks in nests)] and Nest Site 2 [127 nests; 219 eggs; 145 chicks (6 dead chicks in nests)]. Although least terns nested on Nest Site 1 (3 nests), Nest Site 3 (4 nests), and within the Seasonal Ponds (6 nests), 100% of those eggs were depredated.

Based on field surveys, we estimate the number of fledglings at Bolsa Chica was 55 to 65. Nesting and fledgling numbers were lower in 2015 than the previous year when we had 301 nests and an estimated 80 fledglings.

Western snowy plover, Charadrius alexandrinus nivosus

This year, our monitors recorded the highest number of nests (n= 92) and fledglings (n=129) on record for Bolsa Chica. The total number of chicks that hatched was 208. In comparison, there were 82 nests; 211 chicks; and 113 fledglings during 2014—which was also a very good year for snowy plovers.

Ridgway’s rail, Rallus obsoletus (formerly light-footed clapper rail)

Ridgway’s rail breeding activity was observed and photographed Mr. Steven Eric Smith, an experienced naturalist and photographer. According to Mr. Smith, there were three breeding pairs and two unpaired adults that he believed to be males; thus, the adult population on the reserve consisted of 8 individuals. During 2015, a combined total of 20 rail chicks was produced, and Mr. Smith estimated that 10 to 11 of those chicks survived to fledgling age.

Kelly O’Reilly
Environmental Scientist
Bolsa Chica Ecological Reserve
California Department of Fish & Wildlife



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