Frank's Dump West, Hayward Regional Shoreline
Sun, 31 Aug 2003 18:38:59 -0700
From: Dennis Braddy
EastBayBirders,
I figured if a small pond in Alviso warranted two Hudsonian Godwits, then there would probably be several in Frank's Dump West at Hayward Regional Shoreline. I figured wrong.
Nevertheless the shorebirding, particularly in the hour before high tide, was excellent as usual. A truly sedentary birder could have picked a spot midway along the west side of Frank's Dump and scoped 16 species of shorebird including Snowy Plover, Red Knot, Surfbird, Ruddy Turnstone, Black Turnstone, Sanderling, Semipalmated Plover, Willet, Least Sandpiper, Long-billed Curlew, Black-necked Stilt, Black-bellied Plover, Western Sandpiper, American Avocet, Short-billed Dowitcher, and Marbled Godwit.
I counted 40 Least Terns populating one small island. Every plumage was represented including juvenile (brownish U-shaped markings on back feathers), 1st summer (dark carpal bars and dusky primaries), adult breeding (yellow bill, 2 dark primaries, contrasting white forehead) and adult nonbreeding (black bill, pale primaries). Least Terns flying overhead emitted sharp chir-ee-eep calls.
As the late afternoon blow began in earnest, 30+ Snowy Plovers turned into the wind and hunkered down, each in its own tiny divot in a corner of Frank's Dump not flooded by the rising tide.
Dennis Braddy
San Ramon
Late-season woodland birds
Sun, 31 Aug 2003
20:42:03 PDT
From: Bill Gilbert
August and Beyond: The "Quiet" Season for Woodland Birds
For most woodland bird species, the period after nesting (starting in August or late July for many species) characteristically is "quiet." Hormone levels fall, and singing and breeding usually stop, and many birds molt into their basic plumage. Many species seem to "wander," often feeding in mixed flocks, and migrant species leave. Many birders don't bother going into the woods at this time of year (incoming shorebirds may be more exciting). Also, little avian field research seems to have happened during this late season, so relatively little seems to be known about this seasonal period for most bird species.
When I first started looking at Wilson's Warblers (WIWAs) at Tilden Regional Park (Berkeley Hills) I closed down sometime in July, figuring the breeding season was over and my subjects would soon depart. Then a few years ago Emily Strauss and others reported sighting my color-banded WIWAs into August and even September, so I started looking longer. I subsequently learned that most breeding male WIWAs molt on their territories, and usually sing briefly after molt is complete. Also, some females tend late nests, usually with reduced broods (2 young), which they care for by themselves, and which can fledge as late as early August. Finally, I learned (recently) that at least some females without broods hang around their territories into at least late August.
One other interesting thing that has revealed itself from keeping track into August and September is apparent annual variation in post-breeding-season population numbers (not just for WIWAs, but for other species as well). Stated another way, some late-season "quiet periods" are quieter than others. Considering two years, 2001 and this season, the difference seems quite noticeable.
You may remember 2001 as "the year of the Yellow Warbler" (YWAR). Jewel Lake recorded its first breeding pair in recent memory, and the species (apparent migrants) was frequently seen in late July, August and perhaps into September in the East Bay. Not only were YWARs relatively common, but mixed flocks of birds were frequent in the woods (both oak/bay and riparian) at Tilden. Chestnut-backed Chickadees were the most common mixed flock species, but other local and migrant species (Bushtits, vireos, warblers, flycatchers, creepers, etc.) were participants, as were migrant and locally-fledged WIWAs.
This year, by contrast, the woods are much "quieter." In six visits to the Tilden Nature Area in August I saw relatively few WIWAs (average about 1 or 2 per visit), and few other migrants (just one tanager and an "epid" flycatcher, perhaps a Dusky Flycatcher). Even numbers of residents species, including chickadees, seem reduced compared with 2001. I have seen nothing I would consider to be a mixed flock, and have heard no "after-molt singing" from territorial male WIWAs. Finally, the lack of chatter about woodland birds on EBB perhaps suggests others are having similar success, and that the paucity of woodland birds may be more widespread than just Tilden.
The reasons and geographical extent of apparent annual variation in post-breeding-season bird numbers do not seem to be known, and I'm not certain variations themselves are well documented. One possible causal factor for low numbers this year could be the exceptionally heavy late spring rains. Could these have affected insect numbers (food supply for many woodland bird species), especially lepidoptera on oaks and other trees? The fact that resident species, as well as migrants, seem reduced in number suggests that local conditions (and not just conditions at some distant breeding ground) may be affecting things.
Reflecting on the past season, whatever may be affecting numbers of late-season birds also could have affected relative numbers of spring migrants, and even could have impacted the breeding season. I recall seeing just one tanager, and few migrant warblers, during the spring. A possible negative influence (on bird numbers) was not strongly indicated during the WIWA breeding season; territories were reasonably filled and most pairs eventually fledged young (albeit, in 3 cases a cowbird). However, male WIWAs seemed noticeably less vocal this season (singing is known to be related to energy reserves in songbirds), and adult WIWAs seemed to bring more winged adult food than lepidoptera larvae to nests this year (whereas larvae usually predominate).
The paucity of birds during this year's post-breeding-season is especially noticeable, however. This may make sense in that breeding birds tend to be tied to their breeding grounds, no matter how conditions may vary annually, whereas after the breeding season birds might tend to be "free" to travel elsewhere if local conditions are unfavorable.
The post-breeding-season "quiet" period may be scientifically more interesting than might be assumed in that it could be an indicator of overall conditions over a local or broad area during the year. A holistic study of correlates (climatic, food supply, etc.) to variability in post-breeding-season bird numbers could be fruitful. In that regard, I would be interested in learning about annual variations in butterfly numbers; I believe some group(s) do butterfly censuses, just as birders do bird censuses. Can anyone supply information on these? Possibly butterfly numbers vary seasonally in a similar fashion as do moth larvae that feed on our native oaks (and provide an extremely important food source for migrant and breeding birds).
Bill Gilbert