2009 Virginia Plover Summary

The 2009 VPS revealed that the statewide distribution of both species was similar to that observed in the last eleven years.  No Piping Plovers or Wilson’s Plovers were recorded at Dawson Shoals, a small sand shoal between Cedar and Parramore islands, at sites south of the Chesapeake Bay (i.e., Back Bay NWR and False Cape State Park) or on the western Shore of the Bay (i.e., Craney Island and Grandview Beach; Table 1).  Breeding populations of both species of plovers were confined to the barrier islands of Accomack and Northampton Counties.  Eighty-two percent (n = 307) of all Piping Plover adults and 100% (n = 74) of all Wilson’s Plover adults were observed on the northern barrier islands (Assateague Island – Cedar Island; Table 1).  The number of Piping Plover breeding pairs (n = 31) that were observed this year on the southern barrier islands (Parramore Island - Fisherman Island) decreased by 16% from the number (n = 37) reported during the 2008 VPS. 

The 2009 end-of-season Piping Plover breeding pair total, which includes nesting pairs discovered after the VPS, was 193 (Table 2).  This represents a 7% decrease over the 2008 end-of-season total of 208 pairs; which was the highest total reported in Virginia since the species was listed in 1986 (Figure 1).  Intensive productivity studies following the VPS yielded additional Piping Plover pairs on Wallops Island (n = 1), Assawoman Island (n = 2), Metompkin Island (n = 4),  Wreck Island (n = 2), and Ship Shoal Island (n = 2).  Based on 2008/2009 end-of-season pair estimates, the number of Piping Plover pairs decreased on the northern islands this year by 7% and the southern islands by 8% (Figure 2) with greatest declines occurring on Metompkin and Parramore islands, respectively (Table 2).  An additional three pairs of Wilson’s Plovers were discovered during productivity studies in 2009; two on Metompkin Island and one on Assawoman Island.  This brought the end-of-season breeding pair total up to 40, which represents the largest annual population gain since 2000 (Figure 3).  

Piping Plover Productivity
Ninety-one percent (n = 175 pairs) of the statewide Piping Plover population (n = 193 pairs) was measured for breeding success in 2009.  Prior to 2005, Virginia’s productivity studies were confined to the northern islands (Assateague Island – Cedar Island), where the core of Virginia’s breeding population continues to reside.  The inclusion of the southern barrier islands over the past five years contributed considerably to the statewide productivity estimate given the increase in the number of breeding pairs on the lower islands since 2001 (Figure 2).  This effort has also allowed us to begin quantifying differences in reproductive success between the northern and southern portion of the island chain which will help us better understand why over half of Virginia’s breeding population continues to occupy the northern islands.      

Virginia’s 2009 statewide Piping Plover productivity estimate was 1.19 fledged young per pair (Table 3), which is a minimum estimate because the number of young fledged from Wreck Island was unknown.  This year’s estimate represents the first increase in Virginia’s breeding success since 2004 (Figure 4).  All but one barrier island (i.e., Smith Island) experienced an annual increase in productivity this year (Table 3).  Below is a summary of factors that may have influenced this year’s breeding success along the barrier island chain.

Northern Islands: Assateague Island – Cedar Island

According to preliminary data provided by Chincoteague National Wildlife Refuge (CNWR) and USDA-APHIS Wildlife Services, Assateague, Wallops, and Assawoman islands all exhibited annual increases in productivity in 2009 with the greatest gain occurring on Wallops Island (Table 3).  A total of 44 nesting attempts were documented among the 32 breeding pairs monitored on Assateague Island this year, of which 16 (36%) hatched at least one egg.  Of the 28 nests known to have failed, weather contributed to 68% of the observed nest loss while depredation, parental nest abandonment, and unknown causes accounted for the 21%, 4% and 7% of the remaining nest loss, respectively.    Only 44 (30%) of the known number of eggs laid (n = 145) hatched, indicating that egg loss contributed substantially to the low productivity rate of less than one fledged young per pair (Table 3). 

Prior to 2009, Piping Plover reproductive success on Wallops Island was consistently low or non-existent.  In 2009, four nesting pairs collectively fledged 10 chicks, which resulted in the highest productivity rate reported among all of the sites monitored this year.  The plovers traditionally nested on the north end of Wallops Island, which is closed annually to recreational activity during the avian breeding season.  However, in 2009 Piping Plovers nested south of the recreation closure within the beach’s Off Road Vehicle (ORV) zone for the first time.  New moon tides inundated the north end of the island in May, June, and July.  As the tide levels ebbed, large pools of standing water remained on the beach.  As a result, plovers may have moved further south on the island into the ORV zone where the beach was higher in elevation and less susceptible to tidal inundation.  Following management recommendations outlined in the “Public Recreation and ORV Use” section of the 2008 CNWR Piping Plover Management Section 7 and Biological Opinion (USFWS 2008), NASA environmental staff successfully protected nests and broods from human disturbance in the ORV zone (USFWS 2009).  

A total of 27 nesting attempts were reported among the 26 nesting pairs monitored on Assawoman Island, of which 25 (96%) hatched at least one egg.  Of the two nests known to have failed, one was lost to tidal inundation and the other lost to parental nest abandonment.  Forty-one percent of the eggs known to have hatched (n = 76) survived to fledging stage which yielded an estimate of 1.19 fledged young per pair (Table 3).   

Metompkin Island supported 46 Piping Plover breeding pairs in 2009.  This is a 23% decrease from the 60 pairs monitored in 2008 (n = 60), which was the highest number known to occupy the island since the species’ listing in 1986.  A total of 53 nesting attempts were documented this year, of which 74% (n = 39) resulted in the hatching of at least one egg.  A total of eight nests were lost during the 2009 breeding season.  Three were lost to tidal inundation, three were lost to unknown causes, one nest was abandoned, and one nest was depredated by a Ghost Crab (Ocypode quadrata).  Of 39 nests known to have hatched at least one egg, 72% produced at least one fledged young.  Four broods were discovered among pairs identified during the VPS but for which nests were never found.  Collectively, these pairs fledged four young.  The substantial population decrease from 60 pairs in 2008 to 46 pairs in 2009 may have contributed to this year’s increase in reproductive success (Table 3) by reducing intraspecific competition among pairs. 

In 2009, staff from CNWR assumed Piping Plover monitoring responsibilities on the main portion of Cedar Island while staff from The Nature Conservancy’s Virginia Coast Reserve monitored plovers on the detached northern section of the island referred to as Cedar Sandbar.  A combined total of 34 nesting attempts were documented among the 33 breeding pairs monitored, of which 88% (n = 30 nests) hatched at least one egg.  Of the four nests known to have failed, three were lost to weather events and one was  depredated by a Great Black-backed Gull (Larus marinus).  Among the six pairs monitored on Cedar Sandbar, only one young fledged.  Although we have no information on cause, it is possible that a reduction in suitable foraging habitat resulting from erosion and substantial tidal inundation on the north end of Cedar Sandbar may have played a role in the area’s low productivity.

Southern Islands: Wreck Island – Fisherman Island
As in 2008, three pairs of Piping Plovers were documented nesting on Wreck Island in 2009.  At least one additional territory was documented irregularly throughout the season in an area that was continually overwashed and unsuitable for nesting for much of the season.  Young were only observed from one of the four documented nesting attempts.  Since this brood was last checked at 16 days of age, its fledging status was unknown; therefore we reported zero fledged young per pair for Wreck Island (Table 3). 

One pair of Piping Plovers attempted to nest on the south end of Cobb Island in 2009.  The pair was observed at the site with active scrapes on 3 and 15 June but no activity was observed on subsequent visits in July and August.  Due to the infrequency of site visits to Cobb in 2009, we were not able to document whether any eggs or chicks were produced.  However, based on the timing of the observations of the pair with active scrapes, we assume that this pair was attempting to breed and have included it as a failed nesting attempt in our final estimate of nesting pairs.  This represents the first time that Piping Plovers were observed on Cobb Island since 1998.  

Piping Plovers nesting on Ship Shoal Island exhibited the second to highest productivity relative to the other southern islands in 2009 (Table 3).  Eight of the nine nesting attempts found at the egg stage hatched at least one egg and seven of the nine nesting pairs fledged young.  Six pairs nesting towards the south end of the island produced ten of the fledged young; and despite continual and widespread overwash events on the north end of the island, two of the three pairs nesting there succeeded in producing and fledging young late in the season.  Of note was a pair nesting in a dune on the north end, presumably in response to all other suitable habitat in the area being inundated by tides.   
 
Piping Plovers nesting on Myrtle Island exhibited the highest productivity relative to the other southern islands in 2009 (Table 3).  Seven nesting attempts were documented among five nesting pairs.  All seven attempts successfully hatched young, and four of the five pairs fledged young.  Although available habitat on Myrtle continues to decline due to large breached areas that have expanded over the past several years, all five pairs of Piping Plovers were located within one 600m segment of the island that has maintained enough elevation to continue to escape overwash events and expanding breaches.   

Piping Plover productivity declined for the third year in a row on Smith Island and for the first since plovers reestablished themselves on the island in 2004, productivity fell below one fledged young per pair (Table 3).  Smith Island was the only southern barrier island where mammalian predator sign was observed during this breeding season.  Of the 14 nesting attempts found at the egg stage, at least 50% (n=7) hatched at least one egg.  An additional six clutches had an unknown fate due to the infrequency of site visits.  Of 14 pairs documented nesting, only 4 fledged young; however, two pairs successfully raised four young each, which greatly contributed to the overall productivity estimate for the site. 

This year, two pairs of Piping Plovers occurred on Fisherman Island, which marks the forth consecutive year since 1992 that plovers have nested on the island.  Two piping plover chicks fledged this year, increasing the productivity from 0.25 in 2008 to 1.00 chick per pair in 2009 (Table 3).

Wilson’s Plover Productivity
Annual Wilson’s Plover productivity studies have been conducted on Metompkin and Cedar islands from 2004-2008.  While monitoring efforts on Metompkin Island continued in 2009, they were not carried out on Cedar Island because of a shift in staff.  CNWR biologists initiated a Wilson’s Plover productivity study on Assawoman Island this year, which if maintained will make a significant contribution to our understanding of the species breeding ecology in Virginia. 

A total of 22 Wilson’s Plover pairs were monitored on Assawoman and Metompkin Islands, which represented 55% of the statewide population.  Combined estimates of 1.09 fledged chicks per pair were produced at the two sites (Table 4).  The 14 pairs that were monitored on Assawoman collectively fledged 16 young.  Among the eight pairs studied on Metompkin Island, four were found with broods (two broods found during the VPS and two found after the VPS).  Of the four nests that were monitored, all hatched at least one egg and two produced fledged chicks.  The four broods found later in the season yielded at least one fledged young each.  This resulted in a productivity estimate of 1.00 fledged chick per pair (Table 4).  This is the first year since 2004 that Wilson’s Plover productivity on Metompkin Island fell below the estimate reported for Piping Plovers.

Table 1.  Results from the 2009 Virginia Plover Survey.  nd = no data.

Table 2.  A comparison between 2008 and 2009 end-of-season Piping Plover (PIPL) and Wilson’s Plover (WIPL) breeding pair estimates.  End-of-season totals reflect differences at those sites where the number of breeding pairs monitored for productivity exceeded the VPS total except where noted otherwise.   nd = no data.

Table 3.  Piping Plover productivity estimates on Virginia’s barrier islands.  The number of pairs monitored for productivity (n = 175) represents 91% of Virginia’s end-of-season Piping Plover breeding population (n = 193 pairs).  

Table 4.  2009 Wilson’s Plover productivity estimates (est.) for two northern barrier islands monitored for reproductive success.  The number of pairs monitored for productivity (n =22) represented 55% of Virginia’s end-of-season Wilson’s Plover breeding population (n =40 pairs). 

Figure 1.  Annual number of Piping Plover breeding pairs (end-of-season totals) in Virginia, 1986 – 2009.

Figure 2.  Annual number of Piping Plover breeding pairs on the Eastern Shore of Virginia’s barrier islands, 1986 – 2009.   Upper graph presents total number of pairs on the northern barrier islands (Assateague Island – Cedar Island) and the lower graph presents total number of pairs on the southern barrier islands (Parramore Island – Fisherman Island). 

Figure 3.  Annual number of Wilson’s Plover breeding pairs (end-of-season totals) in Virginia, 1988-2009.

Figure 4.  Annual statewide Piping Plover productivity estimates in Virginia, 1990 – 2009.  Annual estimates obtained from ≥ 75% of nests laid each year.

Literature Cited
USFWS.  2008.  Biological Opinion on monitoring and management practices for piping plover (Charadrius melodus), loggerhead sea turtle (Caretta caretta), green sea turtle (Chelonia mydas), leatherback sea turtle (Dermochelys coriacea), and seabeach amaranth (Amaranthus pumilus) on Chincoteague National Wildlife Refuge, Virginia. Chincoteague National Wildlife Report, Chincoteague, VA.

USFWS.  2009.  2009 Piping Plover and Beach Nesting Bird Report. Chincoteague National Wildlife Report, Chincoteague, VA. Unpubl. Rpt. 46 pp.


Acknowledgements
We wish to thank the following individuals who assisted with the annual plover survey and productivity studies:  Frances Ashton, Nicole Bartlett, Ruth Beck, Joelle Buffa, Michael Byrd, Amanda Daisey, Pam Denmon, Nicole Dewberry, Dot Field, Matt Freeman, Marc Gray, Aaron Griffith, Grant Harter, Heather Hollis, David Hughes, Krista Koehn, Sharon Martin, Geralyn Mireles, Christine Petersen, Eva Savage, Brian Scharle, Bill Wills, Sharon Wills and Beth Wright.