2008 Annual Monitoring Report (pdf 10.9MB) - Bolsa Chica ...

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Western Snowy Plover Nesting at Bolsa Chica, 2008 December, 2008 initiated in mid April, one on NTI and one on STI. The third abandoned nest was initiated in mid- July in Cell 19. 14 12 # of Nests 10 8 6 4 2 initiated hatched predated/lost 0 Mar 16-31 Apr 1-15 Apr 16-30 May 1-15 May 16-31 Jun 1-15 Jun 16-30 Survey Time Period Jul 1-15 Jul 16-31 Aug 1-15 Figure 4. Biweekly Western Snowy Plover Nest Initiation, Hatching, & Loss at Bolsa Chica in 2008. The abandoned nest on NTI was caused by harassment of the plover pair by elegant terns. The plovers continuously failed to reach the protection of the ME over their eggs and after 2 days abandoned the nest. In 2007, on NS1, 2 plover nests protected by an ME survived to hatch amongst the elegant terns. The nest abandoned on STI (Nest #19) was incubated by banded female WWYY. Prior to the abandonment of Nest #19, Nest #12 hatched, but the brood was unattended by an adult. The chicks from Nest # 12 gravitated to Nest #19 and, after initially attempting to drive off the chicks, the female (WWYY) began to brood these chicks and to simultaneously incubate her own eggs. It was apparent that she was confused by the situation and the next day after an adult from Nest #12 appeared and brooded its chicks, the female abandoned her Nest #19. The nest in Cell 19, Nest # 65, was abandoned for unknown reasons. Subsequent examination of eggs revealed semi-developed chicks. A total of 193 snowy plover eggs were produced at Bolsa Chica in 2008, with 19 eggs abandoned, predated, or failing to hatch. From the 193 total eggs, 174 chicks were produced. Of these 174 total chicks produced in 2008, a minimum of 57 chicks (32.8%) and a maximum of 109 chicks (62.6%) were estimated to have survived to fledge (Table 2). This is the highest number of hatched nests and potentially the highest number of fledglings recorded at Bolsa Chica. Even the minimum number of fledglings is surpassed only by 2004, 2005, and 2006 (Figure 5). Sixty-two nests survived to hatch with a hatching success rate of 92.5%. This is the highest hatching success rate in all years surveyed with the exception of 2007 at 96.0%. Merkel & Associates, Inc. 11
Western Snowy Plover Nesting at Bolsa Chica, 2008 December, 2008 The total fledgling count was difficult to determine in 2008 due to the nesting activity on NS1; black skimmers, elegant terns, royal terns, Caspian terns, and American avocets all nested on NS1 along with the California least tern and the western snowy plover. During July and August, there was so much activity on the nest site that walking the site to locate nests was no longer possible and all human activity on the site was stopped. The total fledgling count for 2008 was estimated to be between 57 and 109. This minimum count is an increase over the results for 2007 and is comparable to the higher counts in previous years. # Nests 90 80 70 60 50 40 30 20 10 0 Hatched Nests Failed Nests Fledglings 1997* 1998 1999 2000 2001 2002 2003 Year Figure 5. Comparison of Number of Western Snowy Plover Hatched Nests, Failed Nests, and Fledglings 1997-2008 at Bolsa Chica In 2008, 9 dead eggs were observed, excluding eggs in abandoned nests. With 193 total eggs laid in 2008, 4.7% of total eggs were dead eggs. No laboratory analysis was made of these dead eggs. In the previous 10 years the average percent dead eggs is 4.2% (60/437). In this study, when one or more eggs of a clutch hatch, several days are allowed to pass before any egg(s) that may have been abandoned are removed. No apparently abandoned eggs have been seen to hatch. 2004 2005 2006 2007 2008** * fledglings not determined in 1997 ** minimum number of fledglings presented for 2008 BROOD TRACKING Due to the chronological and geographic spacing of each brood, it is often possible to locate and identify individual broods over the period before they fledge. As generally seen in prior years, in 2008 each brood tended to stay together and the males prevented overlap or co-mingling with other broods. There were confrontations between the males if the broods wondered to close together or tried to take advantage of the same resources (see photo below). Broods hatched from NS3 relocated within days to other locations to seek food. Snowy plovers readily used the roads of Bolsa Chica to cover distances of 1/3 to 3/4 mile. In the seasonal ponds, broods would move about or change cells readily but could generally be identified. Broods on NS1 Merkel & Associates, Inc. 12
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2008 Annual Monitoring Report (pdf 10.9MB) - Bolsa Chica ...

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