Philadelphia Vireo at Fort Rosecrans National Cemetery

The Fort Rosecrans National Cemetery [birding site guide here] sits on the top of Point Loma near the end, as this peninsula juts into the Pacific Ocean. Fall migrants, flying at night and perhaps disoriented by coastal fog, often find themselves out over the ocean at dawn. The nearest point of land? Perhaps the green residential area of Point Loma. If they work themselves southward during the day, they'll eventually end up in the cemetery on Point Loma and not want to fly southward over the bay to the low sand spit that is North Island Naval Air Station and Coronado. These tiny waifs will rest, feed, and wait until nightfall to see if atmospheric conditions are right to fly several hundred more miles farther south on their annual trip.

Not every day brings a new set of migrants, but there are at least a few new birds arriving and departing almost every day, all through September and October. On some mornings there is a "fall out" of migrants--that's what you want--the trees dripping with newly arrived birds. Those individual bird watchers who can arrange their schedule to visit several times a week during fall will end up with many migrants, frequently including rather rare birds. In fact, this is the best location in San Diego County for finding rare neotropical migrants--warblers, vireos, flycatchers, orioles, tanagers, grosbeaks, and others.

Thus it was that Gary Nunn discovered a Philadelphia Vireo at Fort Rosecrans National Cemetery on October 2, 2016. [Read about it on Gary's blog here.] It wasn't a very good day for migrants. It was Gary's third circuit around the SE part of the cemetery, repeatedly checking favorite trees, when he struck gold just before 8:00 am. He then announced his find on the San Diego birding listserve.

Point Loma is almost an hour by freeway from my home, so I only visit a couple of times each fall. Fortuitously, I had chosen this exact day to bird in the Tijuana River Valley, and visit Fort Rosecrans cemetery on the way home.

Updated posts to the San Diego birding list indicated the bird had likely flown away, but I stopped anyway. A few birders were milling about the favored Chinese elm that Gary had indicated earlier. "I think I have it!" someone whisper-shouted, and everyone went running. Was that the bird? It kept hiding very well in the little tree. To make matters worse, a very similar-looking Warbling Vireo was working slowly through the branches. But what's that chasing the Warbling Vireo? It looks yellow on the throat and I think it has dark lores. Is that it? Yes! A "life bird"--the first I've ever seen. And photographed to boot.

Philadelphia Vireo. Fort Rosecrans National Cemetery, San Diego, California. October 2, 2016. Greg Gillson.

Swainson's Hawks in Borrego Springs

Swainson's Hawks over Borrego Springs. This photo represents nearly the total
number of Swainson's Hawks I've previously seen in over 40 years of birding!
March 22, 2015. Borrego Springs, California. Greg Gillson.

Although a fairly common breeder early in the 20th Century, Swainson's Hawks no longer breed in southern California. Breeding widely in open country across western North America--even to Alaska, they form large flocks as they migrate to the pampas of Argentina for the winter.

In 2003 Hal Cohen moved to Borrego Springs from the Midwest, where he enjoyed many hawk watches along the shores of the Great Lakes. The West isn't famous for hawk watches like the East and Midwest, but Hal started counting migrating Turkey Vultures in his new home in late March. On April 11th he discovered about 1000 Swainson's Hawks coming into the Borrego Valley to roost at dusk. They fed on caterpillars in the morning, then departed as the thermals formed. It turns out this this is an annual event not previously discovered.

Borrego Valley Hawkwatch site tracks the comings and going of these birds. The official counts start February 15. Peak numbers are reached in mid to late March. The season ends on April 15. This website is great, because the blog tells you if, and how many, new birds entered the Valley that evening and where the roost is, and what strategy is best for viewing the next day based on wind forecasts. Over 9000 Swainson's Hawks were counted during the 2014 season.

Why are they here?

Yep. That's a caterpillar... and a big one, over 3 inches long. It is the caterpillar for the Sphynx Moth. There are literally millions of these juicy grubs crawling everywhere across the desert (see the tracks?) [not to mention the thousands squished on the roads!]. Why? Queue next photo.

In February there were rains on the desert and those seeds that laid dormant for months, or years, came to life. The moths laid eggs, and the caterpillars hatched and were hungry. The Swainson's Hawks took advantage. And the birders followed! (See this recent post on the Borrego Valley Hawkwatch site.)

---

I made a quick visit last weekend to Borrego Springs to locate some desert birds for my county year list. I was most interested in finding Crissal Thrasher in the mesquite there at dawn. I knew I could watch birds at the waste treatment plant and the Mesquite Bosque and be done mid-morning and still have time to possibly see Swainson's Hawks. They had been reported roosting in the evening near the landfill.

After birding the desert scrub I headed over to where the Swainson's Hawks were forecasted to appear. I noted cars parked on the side of Peg Leg Road and people in clumps looking through scopes and binoculars--birders!

There were still a few hawks in the field here, but most had lifted off--almost 150 were in the air, along with ravens and a few vultures. That's 3x the number of all the previous Swainson's Hawks I've ever seen--in over 40 years of birding! I snapped the photo that introduces this post.

The Swainson's Hawks will still be around for a couple more weeks. If you get the chance you should really check it out! I think I'll make plans for next year and take Marlene for a long weekend. Maybe I can get some closer photos of the hawks while they are still perched in their roosting trees or feeding out in the desert.