Tuesday, March 14, 2017

A couple of interesting birds at San Luis Rey River mouth on March First

On March 1st I took an early morning birding trip before work and visited the San Luis Rey River mouth in Oceanside. It was a very chilly, but welcomingly sunny, morning. Heavy rains a couple of days before had water rushing down the river. It was the first time in 3 years that I had seen the river rush straight into the ocean. The lagoon (a river mouth separated from the ocean by a sandbar) west of the Pacific Street bridge with its many cattails was scoured clean. All the cattails were strewn on the beach northward for at least a half mile.

Needless to say, the rushing river didn't have nearly as many birds as the (formerly) shallow lagoon puddle. I assume that within a week the lagoon will reform, though it may take a year or two for the cattails to return. I'll have to watch.

East (inland) of the Pacific Street bridge over the San Luis Rey River I heard both a Sora and Virginia Rail call in the heavy cattails that didn't get washed away. Both are uncommon winter visitors in the county, September-April, though Sora seems easier to find (or at least hear). Also here was the first two of four Black-crowned Night-Herons hunting the muddy river edges or resting in the cattails on the edge of the water.

Since the river mouth was a rushing torrent, I walked down to the beach where the gulls were gathered. It didn't take long to spot two adult Mew Gulls. Mew Gulls are a regular rare wintering species in San Diego County.

Mew Gull
Mew Gull. Oceanside, California. March 1, 2017. Greg Gillson.
The dark eye in the small round head, green legs, and small unmarked yellow-green bill helps identify the adults.

Mew Gull

Most of the wintering gulls on the beach are the large resident Western Gulls and the smaller California Gulls. An adult California Gull is below. The bill of the adult has a red and black spot on the gonys. The chin is the feathered area between the right and left halves of the lower mandible. Where the two halves fuse together is the gonys. A red spot on the gonys is typical for adults of the larger gulls.

California Gull
California Gull
I spy a Black Skimmer with its long primaries and long, candy-corn bill on the beach! They are fairly unusual in San Diego's North County. They prefer larger, shallow estuaries--especially Mission Bay in winter and the salt works in south San Diego Bay for breeding.

Black Skimmers were first recorded in California in 1962. By 1995 about 1200 pairs bred in the state each summer. That number was also an average number of breeding pairs from 2000-2005, but breeding success fluctuates widely from year-to-year. Most breed at the Salton Sea, San Diego Bay, and Bolsa Chica, Orange County.

There is a hint of patterning on the wing coverts, and old, worn, faded primaries on this individual. So I am guessing this is a one-year old bird.

Black Skimmer
Black Skimmer
There was a very pale-headed large gull on the beach. At first I thought it might be something unusual, perhaps a Glaucous-winged Gull hybrid. But after research I believe it is a typical, but very worn, second cycle Western Gull.

Western Gull, second cycle
Western Gull, second-cycle
Finally, the first of season (FOS) (for me) migrant Northern Rough-winged Swallows were working the river and rested close for a nice photograph.

Northern Rough-winged Swallow
Northern Rough-winged Swallow