North American Birds

VOLUME 69 NO3 2016

A Quarterly Journal of Ornithological Record Published by the American Birding Association. The mission of the journal is to provide a complete overview of the changing panorama of our continent’s birdlife.

Issue link: http://nab.aba.org/i/778845

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330 N O R T H A M E R I C A N B I R D S P E L A G I C B I R D S F R O M C R U I S E S H I P S A LO N G T H E PA C I F I C C O A S T May 2007. The record is accepted by the Or- egon Bird Records Committe but is treated as hypothetical or dubious in most publications. LEACH'S STORM-PETREL (Oceanodroma leucorhoa) Common breeder and visitor to deeper, warm- er, and clearer waters well offshore, beyond the central continental slope (Briggs et al. 1987). This is typically the most numerous species of seabird in waters beyond 80 km from land (Figure 19), and the largest numbers occur far offshore, west of the California Current (Ain - ley 1976, P. Pyle, in litt.). Away from breeding areas, it may occur in highly variable numbers from year to year. In most regions, the high - est densities are usually found in summer and early fall, with numbers peaking July– September (Wahl 1975, Ainley 1976). Often there is a fairly abrupt change from dominant Fork-tailed to dominant Leach's when deeper, warmer water is reached. Arrival dates off colo - nies in late winter and early spring are uncer- tain, although "arrivals" to offshore waters may occur already in February (Wahl 1975, Wahl et al. 2005), and 6 birds were off Monterey to Mendocino, CA 20 Mar 2015, and 9 were off Lincoln and Tillamook, OR and 1 off Pacific, WA 2 Apr 2016. Many single-day cruise totals between Humboldt, CA and southern British Columbia later in spring ran upwards to 400- 700/day. Somewhat larger counts included totals of ca. 1000 off Curry to Douglas, OR 3 May 2007, 1425 off Curry to Lincoln, OR 30 Apr 2014, 1825 off Grays Harbor and Jefferson, and farther south 625 off Lincoln to Curry, OR (with 400 at a single slick 70 km off Florence, Lane) 20 May 2016. The total Washington and Oregon breeding population was recent - ly estimated to be only ca. 4000 birds (North American Birds 63: 144). Off Oregon, the largest concentrations of storm-petrels were typically off Curry and Coos. Research cruises have recorded up to 3000 birds off Oregon during August (M. P. Force, in litt.). Numbers drop off after September or early October, although small and occasionally moderate numbers occur irregularly in winter well offshore. Kenyon et al. (2009) noted that at-sea surveys found a few individuals off Brit - ish Columbia during the winter months, al- though by far the greatest numbers were pres- ent between April and October. Cruise ships have encountered high autumn totals of 55 off Tillamook, OR 26 Sep 2011 and, exceptionally, 1000+ off Coos, OR 21 Sep 2010 and 1500+ between 77 km off Lincoln to 32 km off Curry 28 Sep 2015. Fork-tailed Storm-Petrels were recorded on fall cruises as far south as Mon - terey. Three sailings between early Novem- ber and mid-December 2015 encountered as many as 47 birds off Oregon 16 Dec and 35 birds between San Francisco and Monterey, including one flock of 20 birds 75 km south - west of Año Nuevo, San Mateo, CA 17 Dec. [RINGED (HORNBY'S) STORM-PETREL (Oceanodroma hornbyi) There is a sight record of 1 bird by two ob - servers ca. 72 km off Coos Bay, Coos, OR 3 ships off San Francisco, CA 30 Sep 2008, 104 km west of Pistol River Curry, OR 23 Aug 2009, and 51 km off Point Sal, Santa Barba - ra, CA 29 Sep 2015. Several other fall cruise sightings lacked details. FORK-TAILED STORM-PETREL (Oceanodroma furcata) Fairly common to locally common breeder and visitor in waters over 90 m depth (Wahl 1975) from Humboldt , CA northward, rare south to San Francisco, CA, and recorded as far south as southern Monterey (24 Apr 2016). Often there is a fairly abrupt change from dominant Fork-tailed to dominant Leach's when cooler, upwelled shelf water transi - tions to warmer and deeper water. Although exact arrival dates off colonies are uncertain (mid-April?), a total of 70 were 45-90 km off California, Oregon, and Washington 20- 21 Mar 2015. This species is most abundant between southeastern Alaska and northern Vancouver Island (Figure 18). Sample high cruise counts off northern and central British Columbia included 700 on both 6 Jun and 16 Jul 2013, 1000 on 14 May 2014, and 1300 on 31 May 2014; as well as a spectacular post- breeding concentration of 10,000 birds 20- 40 km off northern Vancouver Island 5 Aug 2013. Single-day highs between southern British Columbia and Humboldt were mostly 70-500 birds, with 700 birds from 30-53 km off Clallam to northern Grays Harbor, WA 17 Jul 2013 and 1250 in a small area 35-45 km off Ozette/La Push, Clallam 21 May 2014; Figures 14, 15. Cook's Petrels are found in highly variable numbers from year to year, even from week to week, well off the California coast. Most pelagic survey and small-boat data indicate that they peak off central California during July and August, when cruises through those waters are lacking. Cruise-ship surveys have detected the largest numbers of birds during late April and early May, when as many as 300+ have been recorded in a single day—as photographed here off Monterey County, California, 7 May 2014, left. Cruises also have documented the fairly regular occur- rence of this species as far north as off southern Oregon, including the individual at right, photographed off Curry County 12 July 2015. Photographs by Curtis Marantz [left] and Owen Schmidt [right]

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