ArticlePDF Available

STATUS AND DISTRIBUTION OF COLONIAL WATERBIRDS IN COASTAL VIRGINIA: 2013 BREEDING SEASON

Authors:

Abstract

We conducted a systematic survey of colonial waterbirds in coastal Virginia during the 2013 breeding season. Nearly 800 surveys of 496 waterbird colonies were conducted. Colonies supported an estimated 60,604 breeding pairs of 24 species. Gulls were the most abundant group, with more than 28,000 breeding pairs. Waders and terns accounted for 14,117 and 10,993 pairs, respectively. Laughing Gulls were the most abundant species, representing nearly 40% of the total waterbird community. The barrier island /lagoon system of the Eastern Shore was the most important region for the majority of colonial species encountered. In 2013, this region supported 23 of the 24 species evaluated. The seaside of the Eastern Shore accounted for 54.7% and 27.0% of all breeding pairs and colonies, respectively. For 14 of the 24 species, the region supported more than 50% of the known coastal population. The colonial waterbird community in coastal Virginia has declined by 36.2% in the years between 1993 and 2013. Population estimates for 19 (79%) of 24 species assessed declined during this period. Declines varied considerably among species, with 10 declining more than 40% and 5 declining more than 60%. Cattle Egrets showed the highest loss rate (-96.2%), declining from an estimated 1,459 to only 56 pairs. Five species increased between 1993 and 2013. Dramatic expansions were documented for White Ibis, Great Black-backed Gull, Double-crested Cormorant, and Brown Pelican. INTRODUCTION In Virginia, colonial waterbirds include herons, egrets, ibises, gulls, terns, skimmers, cormorants, and pelicans. These birds share the unusual characteristic of nesting in dense assemblages often in habitats that are physiographically fragile and dynamic. The result of this behavior is that they typically breed in very few locations such that the loss of a few breeding areas may have profound consequences on a population level. Due to their position in the aquatic food web, they are considered to be good indicators of ecosystem health. The most significant threats to colonial waterbirds include human disturbance, predation, habitat loss, and contaminants. Protection of sensitive colonies clearly depends on the availability of timely locational information. Development of strategic management plans to protect these species and breeding areas requires a broader understanding of population trends. For the years prior to the mid-1970s, systematic information on the abundance and distribution of colonial waterbirds in Virginia does not exist. Information during this period is available only from a smattering of nesting records (e.g. Murray 1952), accounts of individual colonies (e.g. Abbott 1955), and area bird lists (e.g. Grey 1950). In 1975 the Virginia Coast Reserve of the Nature Conservancy completed the first comprehensive survey of all of Virginia' s Atlantic barrier islands colonial nesting waterbirds and compiled a complete review of all of the known literature regarding this diverse avian community (Williams 1976). During the 1975 and 1976 breeding seasons, a systematic survey of wading bird colonies in coastal Virginia was completed in association with a broad-based survey covering the entire Atlantic Coast (Custer and Osborn 1977). In 1977, the first systematic survey of all colonial waterbird species was conducted in association with the "Maine to Virginia" project (Erwin and Korschgen 1979). In the early 1980s, an additional survey was conducted in association with a broad status assessment (Spendelow and Patton 1988). From 1975 through 2005, annual surveys of waterbirds were conducted on all of the Virginia coastal barrier islands by Williams et al. (2006). All of these surveys focused primarily on the coastal fringe and did not cover the entire Coastal Plain. In 1993, a systematic survey was conducted, covering the entire Coastal Plain from the outer coastline to the fall line (Watts and Byrd 1998). This survey was the most comprehensive assessment to date of the colonial waterbird community in coastal Virginia. The effort covered 446 colonies supporting an estimated 94,947 pairs of 24 species. Prior to the 1993 survey, a decision was made by the community of agencies and organizations concerned with waterbirds to repeat the survey on ten-year intervals to monitor trends. In keeping with this agreement, the survey was repeated in 2003 (Watts and Byrd 2006). This paper reports on the second ten-year anniversary assessment conducted during the 2013 breeding season. The purpose of this investigation was to generate population estimates for colonial waterbird species nesting in the Coastal Plain of Virginia in 2013. Information compiled is intended (1) to be integrated into biological databases to be used in the environmental review process, (2) to provide information for comparison to past and future surveys for the purpose of assessing long-term population trends, and (3) to be used in the formulation of management recommendations.
Page 12 Vol. 85(2) THERAVEN 2014
STATUS AND DISTRIBUTION OF COLONIAL WATERBIRDS IN COASTAL VIRGINIA: 2013
BREEDING SEASON
BRYAN D. WATTS AND BARTON
J.
PAXTON
Center for Conservation Biology, College of William and Mary, Virginia Commonwealth University,
Williamsburg, VA 23187-8795
ABSTRACT
Wecond ucted asystematic survey of colonial waterbirds
in coastal Virginia during the 2013 breeding season. Nearly
800 surveys of 496 waterbird colonies were conducted.
Colonies supported an estimated 60,604 breeding pairs of
24 species. Gulls were the most abundant group, with more
than 28,000 breeding pairs. Waders and terns accounted for
14,117 and 10,993 pairs, respectively. Laughing Gulls were
the most abundant species, representing nearly 40% of
the total waterbird community. The barrier island /lagoon
system of the Eastern Shore was the most important region
for the majority of colonial species encountered. In 2013,
this region supported 23 of the 24 species evaluated. The
seaside of the Eastern Shore accounted for 54.7% and 27.0%
of all breeding pairs and colonies, respectively. For 14 of
the 24 species, the region supported more than 50% of the
known coastal population.
The colonial waterbird community in coastal Virginia
has declined by 36.2% in the years between 1993 and 2013.
Population estimates for 19 (79%) of 24 species assessed
declined during this period. Declines varied considerably
among species, with 10 declining more than 40% and 5
declining more than 60%. Cattle Egrets showed the highest
loss rate (-96.2%), declining from an estimated 1,459 to only
56 pairs. Five species increased between 1993 and 2013.
Dramatic expansions were documented for White Ibis,
Great Black-backed Gull, Double-crested Cormorant, and
Brown Pelican.
INTRODUCTION
In Virginia, colonial waterbirds include herons, egrets,
ibises, gulls, terns, skimmers, cormorants, and pelicans. These
birds share the unusual characteristic of nesting in dense
assemblages often in habitats that are physiographically
fragile and dynamic. The result of this behavior is that they
typically breed in very few locations such that the loss of a
few breeding areas may have profound consequences on a
population level. Due to their position in the aquatic food
web, they are considered to be good indicators of ecosystem
health. The most significant threats to colonial waterbirds
include human disturbance, predation, habitat loss, and
contaminants. Protection of sensitive colonies clearly
depends on the availability of timely locational information.
Development of strategic management plans to protect these
species and breeding areas requires a broader understanding
of population trends.
For the years prior to the mid-1970s, systematic
information on the abundance and distribution of colonial
waterbirds in Virginia does not exist. Information during
this period is available only from a smattering of nesting
records (e.g. Murray 1952), accounts of individual colonies
(e.g. Abbott 1955), and area bird lists (e.g. Grey 1950). In
1975 the Virginia Coast Reserve of the Nature Conservancy
completed the first comprehensive survey of all ofVirginia' s
Atlantic barrier islands colonial nesting waterbirds and
compiled a complete review of all of the known literature
regarding this diverse avian community (Williams 1976).
During the 1975 and 1976 breeding seasons, a systematic
survey of wading bird colonies in coastal Virginia was
completed in association with a broad-based survey
covering the entire Atlantic Coast (Custer and Osborn
1977). In 1977, the first systematic survey of all colonial
waterbird species was conducted in association with the
"Maine to Virginia" project (Erwin and Korschgen 1979).
In the early 1980s, an additional survey was conducted in
association with a broad status assessment (Spendelow
and Patton 1988). From 1975 through 2005, annual surveys
of waterbirds were conducted on all of the Virginia coastal
barrier islands by Williams et al. (2006). All of these surveys
focused primarily on the coastal fringe and did not cover
the entire Coastal Plain. In 1993, a systematic survey was
conducted, covering the entire Coastal Plain from the
outer coastline to the fall line (Watts and Byrd 1998). This
survey was the most comprehensive assessment to date of
the colonial waterbird community in coastal Virginia. The
effort covered 446 colonies supporting an estimated 94,947
pairs of 24 species. Prior to the 1993 survey, a decision was
made by the community of agencies and organizations
concerned with waterbirds to repeat the survey on ten-year
intervals to monitor trends. In keeping with this agreement,
the survey was repeated in 2003 (Watts and Byrd 2006).
This paper reports on the second ten-year anniversary
assessment conducted during the 2013 breeding season.
The purpose of this investigation was to generate
population estimates for colonial waterbird species nesting
in the Coastal Plain of Virginia in 2013. Information
compiled is intended (1) to be integrated into biological
databases to be used in the environmental review process,
(2) to provide information for comparison to past and
future surveys for the purpose of assessing long-term
population trends, and (3) to be used in the formulation of
management recommendations.
2014
Vol. 85(2)
THE RAVEN
Page 13
METHODS
Field Surveys - An extensive aerial survey was
conducted using a fixed-wing aircraft during early stages
of the 2013 breeding season. All mainland waterways,
barrier islands, Bay islands, and marshlands were
overflown and searched for wading bird colonies. Due
to their wide distribution and large numbers, only the
largest inland reservoirs and farm ponds were surveyed.
Because Great Blue Heron colonies often form near the
headwaters of small streams, a special attempt was made
to follow all tributaries to their origins. Aerial surveys were
conducted by systematically flying over areas at an altitude
of approximately 100-150 m and searching for evidence of
breeding colonies. Once detected, a colony was circled long
enough to allow observers to map the colony location and
estimate its size. All colonies were given a unique alpha-
numeric code and plotted on GPS-enabled laptops loaded
with a current aerial imagery. Groups ofbreeding pairs were
considered independent colonies if they were: (1)separated
from other groups within a continuous habitat by at least
400 m, (2) separated from other groups by a distinctive
barrier, or (3) separated from other groups by a significant
habitat discontinuity (e.g. birds in dune grassland adjacent
to birds in a patch of deciduous saplings).
Follow-up ground counts were conducted for all
locations except inland Great Blue Heron colonies. Great
Blue Heron colonies were widespread and often situated in
remote locations or over extensive swamps. Financial and
logistical constraints did not allow for ground surveys of
these sites.
Population Estimates - Colony size estimates were
based primarily on counts of active nests and occasionally
on the number of adults present. The number of breeding
adults was used when nest counts were impractical or when
deemed inappropriate due to colony disturbance. Colony
size was based on complete counts whenever possible. All
estimates for aerial surveys were performed by the same
observer. Many different observers were involved with
ground surveys. To reduce observer bias across surveys,
data resolution for estimates was reduced by rounding off
reported numbers to the nearest value using the following
graded scale: nearest 5 for <50, nearest 10 for 50-200, nearest
25 for 200-400, nearest 50 for 400-1,000, nearest 100 for
1,000-2,000, and nearest 200 for >2,000. Complete counts
were used when reported without rounding.
Breeding chronology was taken into account when
designing the survey. Coastal marshes and islands supporting
gulls, terns, and allies were flown between mid-May and
mid-Iune. Ground counts of urban areas were conducted
during April, May, June, and July depending on the species
involved. Ground counts of barrier islands, Bay islands, and
marshlands were conducted during June and July.
Due to the differences in breeding phenology and
circumstances, different surveys were used to generate
population estimates for different species. Ground surveys
were used for all urban colonies and colonies on barrier and
Bay islands. Ground surveys were also used for colonies on
marshlands with the exception of extensive gull colonies.
Gull colonies often cover many hectares, making estimation
of nest numbers much easier from the air.
Population estimates are presented in units of breeding
pairs. Breeding pairs were estimated on a colony-by-colony
basis and compiled to generate an overall population
estimate. For colonies surveyed using nest counts or
estimates, a one-to-one relationship between nests and
pairs was assumed. For colonies surveyed using counts
or estimates of adults, a one-to-one relationship between
adults and pairs was assumed. The portion of population
estimates that were based on nests is provided to allow
the reader to recalculate population estimates based on
number of adults.
Geographic Regions - For the presentation of gross
distribution patterns, the Coastal Plain was broken
down into five geographic regions (Figure 1). Regions
included were: 1) Eastern Shore seaside - barrier island/
lagoon system along the seaward margin of the Delmarva
Peninsula northward to the Maryland/Virginia boundary
line, 2) Bayside and Bay islands - western shoreline of the
Delmarva Peninsula to the Maryland/Virginia border,
and Chesapeake Bay islands of Virginia, 3) Urban -
major urban areas of lower tidewater, including the cities
of Virginia Beach, Norfolk, Portsmouth, Chesapeake,
Newport News, and Hampton, 4) Western Shore - south
shoreline of the Potomac River to the south shoreline of the
James River, including all areas from the western shore of
the Chesapeake Bay west to the fall line, and 5) Southside
- lands south of the James River to the Virginia/North
Carolina border, including all land between the Atlantic
Ocean and the fall line (except areas designated as urban).
Soulhsld.
'-- ..•••••••Study
Location
Figure
1.
Map of study area. The Coastal Plain of Virginia was
subdivided into geographic regions including (1) seaside, (2)
Bay islands, (3) urban, (4) western shore, and (5) southside.
Page 14 Vol. 85(2)
THE RAVEN
2014
RESULTS
Population Estimates - A total of 496 different
waterbird colonies was mapped and surveyed during the
2013 breeding season. Colonies contained an estimated
60,604breeding pairs of 24 species (see Appendix, p. 25, for
the species list). Colony size varied from 2 to 8,600 pairs,
with 87.9% of colonies containing less than 100 pairs and
95.9% containing less than 500 pairs. More than 50% of all
colonies larger than 500 pairs were Laughing Gull colonies.
The majority (74%) of colonies contained only one species
and 92.5% contained three species or fewer. Nine mixed-
species heronries contained seven or more species.
Abundance varied widely among species and species
groups (see Table 1, p. 21). Gulls were the most abundant
group with >28,500 breeding pairs. Waders and terns
accounted for 14,117 and 10,993 pairs, respectively.
Although they have declined dramatically, Laughing Gulls
continue to be the most abundant species and were three
times more abundant than any other species, accounting
for nearly 40% of the total colonial nesting waterbird
community. Other than Laughing Gulls, only Great Blue
Herons, Royal Terns and Herring Gulls exceeded 3,000
breeding pairs. The remaining 20 species accounted for less
than 34% of the total breeding pairs.
Geographic Distribution - The barrier island / lagoon
system of the Eastern Shore was the most important region
for the majority of colonial nesting species encountered (see
Table 2, p. 22). In 2013, this region supported 23 of the 24
species evaluated. The only species not documented within
this geographic area was the Green Heron. This species
does breed within the area, but its population is difficult to
assess. The Eastern Shore accounted for 54.7% and 27.0%
of all breeding pairs and colonies, respectively. For 14 of
the 24 species, the region supported more than 50% of the
known coastal population. Many of these species were
found almost exclusively in this region. The number of
species supported by the other geographic regions varied
widely. The Bay region supported 18 species whereas the
urban, western shore and southside regions supported 14,
5 and 2 species, respectively. The Bay region supported
7 species in common with the Eastern Shore that were
not found elsewhere. The Bay region was the dominant
region for the Forster's Tern, Double-crested Cormorant
and the Brown Pelican. Cities included in the urban
region supported substantial populations of Royal Terns,
Sandwich Terns, Common Terns, Least Terns, Laughing
Gulls, Double-crested Cormorants, Great Egrets, Green
Herons, and Yellow-crowned Night Herons. The western
shore supported significant populations of Great Blue
Herons, Great Egrets and Green Herons.
Population Changes - The colonial waterbird
community as a whole in coastal Virginia has declined
by 36.2% since 1993 (see Table 3, p. 23). There was no
change in either the number or type of species breeding
in the area. Population estimates for 19 (79%) of 24 species
assessed declined between 1993 and 2013. Declines varied
considerably among species, with 10species declining more
than 40% and 5 species declining more than 60%. Cattle
Egrets showed the highest loss rate (-96.2%), declining
from an estimated 1,459 to only 56 pairs. Five species
increased between 1993 and 2013. Dramatic expansions
were documented for White Ibis, Great Black-backed Gull,
Double-crested Cormorant, and Brown Pelican. .
Seaside Region - The barrier island /lagoon system
along the seaward edge of the Delmarva Peninsula is the
most important region for colonial waterbirds in Virginia.
Colonial waterbirds have been systematically surveyed
within this geographic area in 1993, 1998, 2003, 2008, and
2013. In the majority of species, comparisons of population
estimates across these years (see Table 4, p. 24) show
consistent trends. Snowy Egret, Cattle Egret, Green Heron,
Yellow-crowned Night Heron, Glossy Ibis, Herring Gull,
Laughing Gull, Gull-billed Tern, Royal Tern, Forster's Tern,
Common Tern, Least Tern, and Black Skimmer all showed
an overall decline across the five surveys. Only species that
have colonized the area since 1970, including White Ibis,
Great Black-backed Gull, Double-crested Cormorant, and
Brown Pelican, have exhibited mostly consistent increases.
Patterns for other species were stable or showed weak
trends.
Of particular note within this region was the nearly 50%
decline in the Laughing Gull population since 2003. This
catastrophic change was most pronounced within historic
strongholds in Northampton County, where the decline in
both area used for nesting and number of breeding pairs
was greater than 80% (Figure 2).
'"
\
..
..
,
...
Laughing Gull Colonies
2003
Laughing Gull Colonies
2013 •
Figure 2. Distribution of Laughing Gull colonies (2003 vs
2013) along the lower seaside of the Delmarva Peninsula.
2014
Vol. 85(2)
THE RAVEN
Page 15
DISCUSSION
During the 2013 breeding season, coastal Virginia
supported a substantial community of colonial waterbirds.
The size of this community exceeded estimates from the
late 1970s (Erwin and Korschgen 1979) but was less than
the 1993 and 2003 estimates (Watts and Byrd 1998, 2006).
The seaside of the Delmarva Peninsula continues to be
the single most important region for colonial waterbirds
in coastal Virginia. However, most populations are
experiencing declines within this region. There is a clear
need to investigate the role of sea-level rise in declines.
The Bay region also supported a diverse community of
species but much lower numbers of individuals compared
to the seaside. Urban areas supported half of all species,
with residential areas supporting significant populations
of Yellow-crowned Night Herons, Great Egrets and Green
Herons. The Hampton Roads Bridge Tunnel southeast
island now supports the most significant seabird colony
in the state, consisting of breeding Great Black-backed
Gulls, Herring Gulls, Laughing Gulls, Gull-billed Terns,
Royal Terns, Sandwich Terns, Common Terns, and Black
Skimmers.
Collectively, wader species declined 24.3% between
1993 and 2013 from an estimated 18,640 pairs to 14,117
pairs. Most of this overall decline was due to the continued
degradation of mixed heronries both on the seaside and Bay
islands. These declines have been ongoing and represent a
loss of some historic colonies during the past two decades.
Other sites may be lost in the next decade. Particularly
notable were reductions in most mid-sized herons. An
interesting development has been the decline in Great
Blue Herons despite a considerable increase in colonies.
Major colonies have either been lost or have fragmented,
resulting in a decline in colony size. The influence of Bald
Eagle recovery on colony dynamics requires investigation.
White Ibis -
Nesting of the White Ibis was first confirmed
in Virginia in 1977 on Fisherman Island (Frohring and Beck
1978). Breeding has been restricted to the barrier islands.
Breeding areas have been surveyed each year since 1975
(Williams et al. 1990, 2006). Until recent years, birds were
associated exclusively with a mixed-species heronry on
Fisherman Island, with little indication of further expansion
(Williams et al. 1992). This heronry was abandoned in
2002 (Williams et al. 2003) and has not been used since.
In 2000, this pattern changed when birds appeared in the
Cobb-Island heronry (Williams et al. 2001). This event
was followed in 2001 when the Wreck-Island heronry
was colonized (Williams et al. 2002). In 2005, White Ibis
colonized the heronry on Chimney Pole Marsh (Williams
et al. 2006) and then the colony on Wire Narrows (Williams
2010). The population has grown from 3 pairs in 1993 to 369
pairs in 2013. Further expansion is likely, and colonization
should be expected in other large heronries along the
seaside and possibly within the upper Bay islands.
Glossy Ibis -
The Glossy Ibis was first found breeding
in Virginia on Hog Island in 1956 (Bock and Terborgh
1957). The breeding population increased dramatically
throughout the 1960s, reaching a high by the mid-1970s
(Custer and Osborn 1977). Since this time, the species
has steadily declined on the barrier islands (Williams et
al. 1990; Watts and Byrd 2006). By 1993, the coastal plain
population had been reduced by more than 50% from
historic highs (Watts and Byrd 1998). Between 1993 and
2013, the population has declined by 52%. Of particular
importance moving forward is the ongoing erosion of sites
supporting mixed heronries on the Bay islands.
Great Blue Heron -
The Virginia population of Great Blue
Herons has increased dramatically since the 1960s. In 1964,
only 5 colonies of this species were known for coastal
Virginia. In 1975, 15 colonies were surveyed, containing
more than 2,400 pairs (Custer and Osborn 1977). In 1984, 31
colonies were known, supporting nearly 3,600 pairs (Beck
unpublished data). In 1993,156 colonies were documented,
supporting more than 9,000 pairs. In 2003, 202 colonies
were documented, supporting 9,136 pairs. The 2013 survey
represents the first time in more than 40 years that a
decline has been documented in the number of pairs. The
population declined 14.5% since the high of 2003 despite
a substantial (165%) increase in the number of colonies
since 1993. This pattern is the result of fragmentation of
larger colonies and has resulted in a decline in the average
colony size. The underlying cause for the fragmentation is
unclear, but it is notable that in 2011 approximately 25%
of colonies supported at least one pair of nesting Bald
Eagles (Watts, unpublished data). The role of Bald Eagles
in colony dynamics warrants investigation. In addition to
the fragmentation, there has been a loss of historic colonies
over the 20-year period. Many major colonies from the
1970s and 1980s are no longer present.
Great Egret -
The Virginia population of Great Egrets has
increased more than 3 fold in the past 30 years. Trends
have been similar to the Great Blue Heron, but unlike
Great Blues the trend seems to be continuing. This species
has historically had a breeding distribution skewed to the
coast. Over the past 20 years, an increasing number have
colonized inland Great Blue colonies, particularly within
the extensive swamps of the Chickahominy, Blackwater,
Nottoway, and Meherrin drainages. Aside from the
advances toward the fall line, the population in most other
regions is experiencing stress. Several urban colonies have
been lost over the past 30 years (Watts, unpublished data)
as residential neighborhoods move them out. Although
this process is continuing, the birds seem to be resilient
and continue to find new places to nest. Declines on both
the seaside and on Bay islands appear to be solely due to
substrate loss related to erosion. This process is continuing,
and further declines should be expected within these areas
if habitat is not stabilized.
Page 16 Vol. 85(2)
THE
RAVEN
2014
Snowy Egret -
Historically, Snowy Egrets bred as far north
as New England. However, by the turn of the century,
demand from the millinery trade had resulted in a
contraction of the breeding range down to North Carolina
(Ogden 1978). The first evidence of recolonization was in
1941, when birds were discovered breeding on the seaside
of the Delmarva (Murray 1952). By the mid-1950s, this
species was documented in all geographic areas of coastal
Virginia except the southside region (e.g. Grey 1950,
Abbott 1955). However, since the 1970s, breeding has been
restricted to the seaside of the Delmarva and the offshore
islands of the upper Bay. Numbers have declined steadily
on the barrier islands since the mid-1970s. The coastal-
plain-wide survey in 1993 was comparable to the surveys
of the mid-1970s (Custer and Osborn 1977, Watts and Byrd
1998). Between 1993 and 2013 the population has declined
by more than 60%. However, the population was relatively
stable between 2003 and 2013. Loss of nesting substrate on
the seaside and on bay islands continues to be a concern.
The colony surveyed on an islet of the Guinea Marshes of
Gloucester County in 2003 was lost before 2008 due to loss
of nest substrate. The species continues to nest on Mumford
Island on the York River though the island continues to be
impacted by storm erosion.
Tricolored Heron-
The Tricolored Heron was first documented
to nest in Virginia when breeding birds were discovered
on the seaside of the Delmarva in 1941 (Montagna and
Wimsatt 1942, Murray 1952). Colonization of Virginia was
part of a broader northward range expansion that occurred
between the 1940s and 1970s (Ogden 1978). In Virginia, the
population apparently increased to a high during the 1950s
then plateaued, remaining at that size through the 1970s
(Erwin and Korschgen 1979). The species has declined on
the barrier islands since that time (Williams et al. 1990).
The population estimate of 1993 (Watts and Byrd 1998) was
more than 50% reduced from that of the mid-1970s (Custer
and Osborn 1977). Following a decline of 34% between
1993 and 2003, the population has increased 41%, bringing
it back to within 6.5% of the 1993 estimate. Like the other
mid-sized waders, this species is vulnerable to ongoing
habitat changes.
Little Blue Heron -
Little Blue Herons were one of the most
abundant waders along the Atlantic Coast from the 1930s
to the 1950s (Ogden 1978). Historic breeding records for
this species exist for all of the geographic regions of coastal
Virginia (Grey 1950, Murray 1952, Abbott 1955). The
species declined dramatically from the 1950s to the 1970s
(Erwin and Korschgen 1979) and is now found only on the
seaside of the Delmarva Peninsula and within 2 colonies
on Chesapeake Bay islands. From 1993 to 2013, Little Blue
Herons declined by an estimated 52.4%, including a 42.5%
decline since 2003. The decline continues to be widespread,
with very few pairs now on the Bay islands and reduced
numbers in most of the seaside strongholds.
Cattle Egret -
The Cattle Egret was first found breeding in
Virginia in 1961 (Scott and Cutler 1961). Colonization of
Virginia was part of a rapid, broad-front range expansion
that followed first establishment in North America in
1953 (Crosby 1972, Telfair 1994). The Virginia population
increased rapidly during the 1960s. Although there has
been considerable year-to-year variation on the barrier
islands, numbers have declined since the mid-1970s, with
precipitous declines since the mid-1990s. Cattle Egrets
experienced a dramatic decline between 1993 and 2013
within all breeding areas. Only 8 pairs were detected on
islands within the Chesapeake Bay. Birds disappeared from
the Hopewell colony on the James River in the mid-1990s
and have never returned. Birds are now restricted to just 3
colonies in Virginia. It now appears likely that this species
will be lost from the state.
Green Heron -
Green Herons nest widely throughout the
Coastal Plain. Due to their broad distribution and cryptic
coloration, none of the colonial waterbird surveys have
adequately covered this species. Population estimates are
inadequate to assess trends outside of the heronries that are
surveyed regularly. Within the heronries that are surveyed
regularly, Green Herons have declined dramatically within
both the barrier island/lagoon system and the Chesapeake
Bay islands. More moderate declines were documented in
the traditional colonies within urban areas.
Black-crowned Night Heron -
The breeding population of
Black-crowned Night Herons in coastal Virginia declined
by an estimated 80% between 1975 (Custer and Osborn
1977) and 1993 (Watts and Byrd 1998). However, the
species increased throughout the broader Coastal Plain
between 1993 and 2003, and this trend continued through
the 2008 survey. Much of this increase may be attributed to
expansion of numbers within the Watts Island and Tangier
Island colonies since 2003. Between 2003 and 2013, Black-
crowns have declined by 44%, resulting in a 32% decline
since 1993. The only strongholds remaining for the species
in 2013 were Wreck Island along the Seaside and Watts
Island in the Bay.
Yellow-crowned Night Heron -
The Yellow-crowned Night
Heron likely bred in Virginia in the 1800sbut was apparently
absent by the early 1900s. The first modern breeding record
for Virginia was in 1944 in King William County (EM. Jones
unpublished report). This event corresponds with a range
expansion from the Southeast northward toNew England
(Watts 1995). In Virginia, Yellow-crowneds increased
within urban areas of Norfolk, Hampton, Virginia Beach,
and Portsmouth at least through the early 1990s (Watts
unpublished data). Since 1993, the population has declined
by 23%. This decline is primarily due to the loss of birds
within seaside heronries and to a lesser extent on Bay
islands. Despite disruption by residents within urban areas
that have caused distribution shifts, the species appears to
be doing well in lower Tidewater.
2014 Vol. 85(2)
THE RAVEN
Page 17
As a group, gulls declined by more than 47.6% over the
20-year period from an estimated 54,702 breeding pairs in
1993 to 28,658 in 2013. This decline was due almost entirely
to the catastrophic decline in Laughing Gulls between 2003
and 2013. Herring Gulls continue their long decline. Great
Black-backed Gulls increased dramatically over the period.
Great Black-backed Gull -
In 1970, the Great Black-backed
Gull was found breeding on Fisherman Island (Scott
and Cutler 1970). This event was part of a broader range
expansion that began in the early 1900s and has moved
down the Atlantic Coast (Good 1998). Since the 1970s, this
species has rapidly colonized other locations on both the
seaside (Williams et a1. 2006) and Chesapeake Bay islands
(Brinker et a1.2007) Between 1993 and 2013, the population
has more than doubled in size and continued to expand
in distribution. Although the stronghold continues to
be within the seaside, 15 colonies now occur within the
Virginia portion of the Chesapeake Bay. Colonization of
the Hampton Roads Tunnel Island since 2003 represents
the first toehold in the lower portion of the Bay.The colony
located in 2008 on a small islet along the Guinea Marshes in
Gloucester County was not occupied in 2013. The islet had
experienced considerable storm erosion.
Herring Gull -
A single Herring Gull nest was found on the
seaside near Cobb Island in 1948 (Buckalew 1948). By 1977,
9 colonies containing more than 2,900 pairs were reported
(Erwin and Korschgen 1979). The 1993 survey located 35
colonies supporting an estimated 8,800 pairs. The breeding
population on the barrier islands apparently reached a
high in the late 1980s and has shown evidence of a decline
since that time (Williams et a1.2006, Watts and Byrd 2006).
Between 1993 and 2013, the Coastal Plain population
declined by an estimated 62.2% or an additional 26% since
2003. Consistent declines were observed in both regions
where breeding was documented in 1993. New colonies
have been recorded in the lower Bay since 2003, including
on the Hampton Roads Tunnel Island and near the mouth
of the York River (Watts and Byrd 2006). The colony on the
islet along the Guinea Marshes was not occupied in 2013.
Laughing Gull -
Virginia has apparently been a stronghold
for breeding Laughing Gulls for centuries. This species has
been the numerically dominant colonial waterbird during
all comprehensive surveys conducted of the Coastal
Plain. Between 1977 and 1993, there was a considerable
increase in population estimates. Between 1993 and
1998, there was a very small decline in numbers on the
seaside of the Delmarva Peninsula (Truitt and Schwab
2001). The population decline between 2003 and 2013 was
catastrophic and the most significant result of the 2013
survey. Historic colony sites within the southern portion
of the Delmarva seaside have now been abandoned for
several years. Evidence of stress is now being seen within
the topographically higher colonies in Accomack County
along the Chincoteague Causeway. Collectively, the
patterns of decline suggest impacts by tidal flooding that
require further investigation.
As a group, terns declined 38.2% over the 20-year period
from an estimated 17,785 to 10,993 breeding pairs. There
were no exceptions to the general pattern. All species
experienced declines ranging from 6 to 70%.
Gull-billed Tern -
The Gull-billed Tern has experienced
extreme population swings in coastal Virginia over the past
200 years (Parnell et a1.1995). In the mid-1800s this species
was considered to be abundant along the barrier islands.
By the late 1800s and early 1900s, they had been reduced
to very low numbers by hunters supplying the millinery
trade (Bailey 1913). Throughout the early 1900s, numbers
remained very low (Austin 1932). By the mid-1970s,
numbers appear to have recovered and were comparable
to those of the 1800s. By 1993, the population had declined
once again to approximately 20% of 1970s levels (Watts
and Byrd 1998). Between 1993 and 2013, the number of
occupied colonies declined from 30 to 8, and the number
of breeding pairs declined by 51.5%. The species is now
nearly restricted to shell piles within the barrier island/
lagoon system and to a single colony on the Hampton
Roads Bridge Tunnel.
Caspian Tern -
There is some evidence that Caspian Terns
once bred in greater numbers along the Virginia barrier
islands than they have from 1900 to present (reviewed by
Weske et a1. 1977). Egging and hunting apparently reduced
their numbers in the 1880s to a low from which they have
never fully recovered. Since 1900, Caspians have been
documented in very low numbers breeding in scattered
locations along the seaside and occasionally on Chesapeake
Bay islands. They appear to be present consistently since
the mid-1970s. In 1993 only 7 pairs were documented in 5
locations. During the 2003 survey, only a single pair was
documented. In 2008, 2 pairs were documented on Clump
Island in the upper Bay. In 2013, pairs were found only
within the northern portion of the barrier island/lagoon
system. Although the Virginia population of Caspians
appears to be very small in recent decades, it is also likely
that this species is not well surveyed. Unlike Royal and
Sandwich Terns that nest in large conspicuous colonies,
Caspians often nest as single pairs on shell piles in the
lagoon system or within small colonies of other smaller
terns.
Royal Tern -
In Virginia, Royal Terns 'have apparently
always been the most abundant of the large terns. Like
many of the other terns, their numbers have fluctuated
widely through the years due to natural and human
perturbations. This species also appears to move over a
larger spatial scale such that local population patterns may
reflect movements rather than population changes. This
possibility is supported by wide fluctuations in adjacent
states (D. Brinker, S. Cameron unpublished data). Royal
Terns have declined on the barrier islands since the early
Page 18 Vol. 85(2)
THE RAVEN
2014
1980s (Williams et al. 2006). The population estimate
for the broader Coastal Plain in 1993 was comparable to
estimates from the mid-1970s (Erwin and Korschgen 1979).
Since 1993, the number of breeding pairs has declined
14.9%. Since 2003, numbers have increased due entirely to
the establishment of birds on the Hampton Roads Bridge
Tunnel Island. Many of the pairs of Royal Terns currently
breeding on the Hampton Roads Bridge Tunnel Island
are likely pairs that formerly bred on the barrier islands.
In 2013, the Hampton Roads Bridge Tunnel Island site
supported 97.5% of the state population.
Sandwich Tern -
Virginia and occasionally Maryland
represent the northern range limit for breeding Sandwich
Terns. There is no evidence that this species was ever
a common breeder in Virginia. Scattered records in the
late 1800s and early 1900s imply that this species was an
uncommon nester associated with Royal Tern colonies on
the barrier islands (records reviewed by Weske et al. 1977).
There is a paucity of reports throughout the middle 1900s
until the late 1960s, when the species was discovered nesting
again on the barrier islands (Buckley and Buckley 1968).
Breeding has been consistent on the barrier islands since
the mid-1970s but has involved relatively few individuals.
Numbers documented during the annual barrier island
survey have fluctuated widely since the mid-1970s
(Williams et al. unpublished data). The change from 30
pairs in 1993 to 7 pairs in 2003 to 100 pairs in 2008 and back
to 28 pairs in 2013 reflects the dynamics of their occurrence
in Virginia. Since 2010 this species has successfully nested
among Royal Terns on the Hampton Roads Bridge Tunnel
(Williams 2010, 2011, 2012, 2013).
Forster's Tern -
Like many of the other colonial species that
nested historically in coastal Virginia, Forster's Terns were
greatly impacted by market hunting from the 1870s though
approximately 1910 (Howell 1911, Austin 1932). Due to
their nesting habits, the status of Forster's Terns was less
known compared to other tern species. Forster's nest
in scattered colonies within the lagoon system on wrack
deposited in the marshes or on other topographic highs.
Their distributions are subject to change depending on the
availability of nesting substrate. This makes them difficult
to survey effectively. The first comprehensive survey of
Forster's was in 1977 (Erwin and Korschgen 1977). By
1993, numbers appeared to have doubled (Watts and Byrd
1998). Between 1993 and 2013, estimated population size
declined by 17.3%. The concentration of large colonies on
Bay islands is a trend that is continuing.
Common Tern -
Historically, the Common Tern nested
throughout coastal Virginia wherever there was suitable
substrate away from predators. Like many of the other
species, Common Terns were hunted to very low numbers
by the turn of the 20th century, but there were signs of
recovery by the early 1930s (Austin 1932). Since the 1960s,
Common Tern colonies have been documented in many
areas of the Coastal Plain. However, over the past 20 years
colonies have disappeared from the western shore and
lower tidewater. Since the 1980s, Common Terns have
shown overall declines on the barrier islands (Williams
et al. 2006). However, declines on the islands were
compensated for by the formation of the largest colony in
the state on the Hampton Roads Tunnel Island such that
estimates from 1977 (Erwin and Korschgen 1979) and. 1993
(Watts and Byrd 1998) were comparable. Between 1993 and
2013, Common Terns declined by 70.7% in coastal Virginia.
Considerable declines have been documented in all 3
geographic regions that supported colonies in 1993. Much
of the overall decline was accounted for by the recent losses
within the tunnel island colony. The invasion of Laughing
Gulls within this site prior to the 2003 survey reduced the
Common Tern population by more than 75%. As of 2013,
this loss has not been absorbed in other regions.
Least Tern -
Historically, Least Tern colonies have been
documented throughout many areas of coastal Virginia,
including up major tributaries to near tidal fresh waters.
Abundant on the barrier islands, this species was hunted
relentlessly during the late 1800s to near extirpation
(Chapman 1899, Howell 1911). After release from hunting
pressures, Least Terns rebounded rapidly. Numbers appear
to have reached a high in the early 1980s and then declined
steadily over the next 20 years (Beck et al. 1990). Between
1993 and 2013, the population declined 21% from 1171 to
925 breeding pairs. In 2007, rooftop nesting was confirmed
at Patrick Henry Mall and Lynnhaven Mall; the latter site
had apparently been utilized by nesting Least Terns for the
previous six years (Williams 2007). The formation of rooftop
colonies has been reported throughout the Southeast and
has been anticipated for many years in Virginia. It is possible
that additional colonies exist within lower tidewater or
elsewhere and have not been discovered. Such colonies
are subject to severe heat stress and active management is
required to improve productivity.
Black Skimmer -
The Black Skimmer appears to have been
a common nester on the barrier islands for as far back as
records are available. Due to their coloration, skimmers
were not valued in the millinery trade and so were not
hunted as actively as many of the other beach-nesting
species. They also were favored by the locals and so did not
experience the same degree of pressure from eggers. From
most accounts, Black Skimmers were one of the numeric ally
dominant species on the barrier islands throughout most
of the 20th century. However, between the mid-1970s and
the 1990s, numbers on the barrier islands were reduced by
70%. This decline continued between 1993 and 2013 as the
coastal population declined 51.4% from an estimated 3,098
to 1,506 breeding pairs. The population along the barrier
islands appears to have stabilized between 2008 and 2013.
Double-crested Cormorant -
Breeding of the Double-crested
Cormorant in Virginia was first confirmed in 1978 on a
2014 Vol. 85(2)
THE RAVEN
Page 19
small vegetated island in the James River near Hopewell
(Blem et al. 1980). Throughout the 20th century, cormorants
experienced wide fluctuations in numbers and distribution
throughout their range (Hatch 1984). Colonization of
Virginia represents an expansion beyond the historic range
following a low during the DDT era (1940s-1972) (Hatch
and Weseloh 1999). After 1984, the Virginia population
expanded rapidly, and by 1995 there were 5 colonies
containing more than 400 pairs (Watts and Bradshaw 1996).
The seaside of the Delmarva was not colonized until 1995.
Between 1993 and 2013, the population increased by 712%
from 354 to 2,876 pairs. Most of this increase is accounted
for by the rapid expansion of the Shanks Island colony
in the Chesapeake Bay. The colony has expanded from 6
pairs in 1993 to 907 pairs in 2003 to 1,636 in 2008 to 2,369
in 2013. Four colonies now exist on the seaside, including
3 on duck blinds in Chincoteague Bay. It seems likely that
this species will expand on the seaside as the breeding of
Brown Pelicans expands.
Brawn Pelican -
The Brown Pelican was first found breeding
in Virginia on Fisherman Island in 1987 (Williams 1989).
During this same year, birds were also found nesting
on Metompkin Island (Williams 1989). Since that year,
breeding on the barrier islands has been restricted to
Fisherman Island. In 1992,an additional colony was formed
in the upper Chesapeake Bay on Shanks Island north of
Tangier (Brinker, pers. comm.). In recent years, a colony
has formed on Sandy Island near the north end of Hog
Island on the seaside. Colonization of Virginia represents
a northward range expansion from North Carolina that
extends beyond the historic range and follows recovery of
southeastern populations from the effects of contaminants.
Since its discovery, the Shanks Island colony has grown
exponentially, apparently fueled by continued immigration.
In 1993, there were only 53 pairs documented in this colony
(Watts and Byrd 1998). By 1999, the colony supported 913
breeding pairs (Watts 2000). Between 1993 and 2013 the
Virginia population increased 567% from an estimated
368 to 2,454 breeding pairs. Growth in the Shank's Island
colony has slowed in the past few years, suggesting that
it may be reaching capacity. Distribution along the barrier
islands is dynamic, with colonies shifting between years.
ACKNOWLEDGEMENTS
Many individuals and organizations contributed to the
success of the 2013 colonial waterbird survey in Virginia. We
very much appreciate and admire the broad commitment by
agencies and individuals to this bird community. Captain
Fuzzzo Shermer and Jim Reed provided expert flying
services. We thank the many observers who participated in
ground surveys, including
R
Boettcher, A Wilke,
R
Beck,
K. Birker, M. Byrd, E. Carsen, M. Charlesworth, B. Farmer,
J. Harvie, J. Joeckel, E. Larson, K. Lewicki, J. Lewis, A
Lipford,
R
Lukei, J. McClain, B. Miller, C. Miller, E.Mojica,
1. Moore, S. Rice, J. Tamuatee, J. Tarwater, M. Watts, and
S. Whealton. Erica Lawler provided fiscal management
from the College of William
&
Mary. Financial support was
provided by the Virginia Department of Game
&
Inland
Fisheries, The Center for Conservation Biology, The Nature
Conservancy, the Virginia Department of Transportation,
and the u.s. Army Corps of Engineers. Additional agency
partners include the u.S. Fish and Wildlife Service and the
Natural Heritage Program of the Virginia Department of
Conservation and Recreation. We thank two anonymous
reviewers for their valuable comments on the manuscript.
LITERATURE CITED
Abbott, J. M. 1955. The Hollis Marsh Island heronry,
Westmoreland County, Virginia. The Raven 26:102-103.
Austin, O.
1.,
Jr. 1932. Cobb Island. Bird-Banding 8:12-25.
Bailey, H. H. 1913. The birds of Virginia. J.P. Bell, Co!, Inc.
Lynchburg, VA
Beck,
R
A, J. W. Akers, J. W. Via, and B. Williams. 1990.
Status and distribution of the Least Tern in Virginia -
1975 to 1988. Virginia Journal of Science. 41:404-418.
Blem, C.
R,
W. H. Gutzke, and C. Filemyr. 1980. First
breeding of the Double-crested Cormorant in Virginia.
Wilson Bulletin 92:127-128.
Bock, W. and J. Terborgh. 1957. Breeding of the Glossy Ibis
in Virginia. Bird Banding 28:38.
Brinker, D. F., J. M. McCann, B. Williams and B. D. Watts.
2007. Colonial nesting seabirds in the Chesapeake Bay
Region: Where have we been and where are we going?
Waterbirds 30 (Special Publication 1):93-104.
Buckalew, J. H. 1948. Nesting of the Herring Gull in
Virginia. Wood Thrush 4:22.
Buckley, P. A and F.G. Buckley. 1968. The current status of
certain birds in the Virginia Capes area. II. April 1967-
July 1968 observations. The Raven 39:27-40.
Chapman, F. 1899. The passing of the tern. Bird-Lore 2:204-
206.
Crosby, G. T. 1972. Spread of the Cattle Egret in the Western
Hemisphere. Bird Banding 43:205-212.
Custer, T. W. and
R
G. Osborn. 1977. Wading birds as
biological indicators: 1975 colony survey. U'S. Fish and
Wildlife Service Special Scientific Report - Wildlife No.
206.28 pp.
Erwin,
R
M. and C. E. Korschgen. 1979. Coastal waterbird
colonies: Maine to Virginia, 1977. An atlas showing
colony locations and species composition. U.S. Fish
and Wildlife Service FWS/OBS-79/08.
Frohring, P. C. and
R
A. Beck. 1978. First breeding record of
the White Ibis (Eudocimus albus) in Virginia. American
Birds 32:l.
Good, T. P. 1998. Great Black-backed Gull (Larus marinus).
In The Birds of North America, No. 330 (A Poole
and F. Gill, Eds.). The Birds of North America, Inc.,
Philadelphia, PA
Page 20 Vol. 85(2)
THE RAVEN
2014
Grey, J. H., Jr. 1950. Birds of the Cape Henry area. The
Raven 21:30-69.
Hatch, J. J. 1984. Rapid increase in Double-crested
Cormorants nesting in southern New England.
American Birds 38:899-902.
Hatch, J. J., and D. V. Weseloh. 1999. Double-crested
Cormorant (Phalacrocorax auritus). In The Birds of
North America, No. 441 (A. Poole and
E
Gill, Eds.). The
Birds of North America, Inc., Philadelphia, PA.
Howell, A. B. 1911. A comparative study at Cobb's Island,
VA.Auk 28:449-453.
Montagna, W. and W. A. Wimsatt. 1942. Bird records from
Virginia. Auk 59:434-436.
Murray, J. J. 1952. A checklist of the birds of Virginia.
Virginia Society of Ornithology.
Ogden, J. C. 1978. Recent population trends of colonial
wading birds on the Atlantic and Gulf Coastal Plains.
Pp. 137-154 in: Wading birds. National Audubon
Society Research Report No. 7 (A. Sprunt IV, J. C.
Ogden, and S. Winckler, Eds.) National Audubon
Society, New York, New York.
Parnell, J. E, R. M. Erwin, and K. C. Molina. 1995. Gull-
billed Tern (Sterna nilotica). In The Birds of North
America, No. 140 (A. Poole and
E
Gill, Eds.). The
Academy of Natural Sciences, Philadelphia and The
American Ornithologists' Union, Washington, D.C.
Scott,
E
R. and D. A. Cutler. 1961. Middle Atlantic coast
region. Audubon Field Notes 15:455. 458.
Scott,
E
R. and D. A. Cutler. 1970. Middle Atlantic Coast
region. American Birds 24:688-670.
Spendelow, J. A. and S. R. Patton. 1988. National atlas of
coastal waterbird colonies in the contiguous United
States: 1976-1982. U.S. Fish and Wildlife Service
Biological Report 88(5).
Telfair, R. C. II. 1994. Cattle Egret (Bubulcus ibis). In The
Birds of North America, No. 113 (A. Poole and
E
Gill,
Eds.). Philadelphia: The Academy of Natural Sciences;
Washington, D.
C:
The American Ornithologists'
Union.
Truitt, B. R. and D. J. Schwab. 2001. 1998 Eastern Shore
seaside barrier island / lagoon colonial waterbird
~urvey. The Raven 72:126-131.
Watts, B.D.1995. Yellow-crowned Night Heron (Nyctanassa
violacea). In The Birds of North America, No. 161 (A.
Poole and E Gill, Eds.) Academy of Natural Sciences,
Philadelphia, PA and the American Ornithologists
Union, Washington, D.C.
Watts, B. D. 2000. A study of waterbirds in Shanks
Creek: An investigation on Smith Island, MD.
Center for Conservation Biology Technical Report
Series, CCBTR-00-12. College of William and Mary,
Williamsburg, VA. 30 pp.
Watts, B.D. and D. S.Bradshaw. 1996.Population expansion
by Double-crested Cormorants in Virginia. The Raven
67:75-78.
Watts, B. D. and M. A. Byrd. 1998. Status and distribution
of colonial waterbirds in coastal Virginia. The Raven
69:20-31.
Watts, B. D. and M. A. Byrd. 2006. Status and distribution
of colonial waterbirds in coastal Virginia: The 2003
breeding season. The Raven 77:3-22.
Watts, B. D. and B. J. Paxton. 2009. Status and distribution
of colonial waterbirds in coastal Virginia: 2009breeding
season. CCBTR-09-03. Center for Conservation Biology,
College of William and Mary /Virginia Commonwealth
University, Williamsburg, VA 21 pp.
Weske, J. S., R. B. Clapp, and J. M. Sheppard. 1977. Breeding
records of Sandwich and Caspian Terns in Virginia and
Maryland. The Raven 48:59-65.
Williams, B. 1976. Analysis of the past and present status
of the beach nesting and colonial birds of the Virginia
Coast Reserve. In Virginia Coast Reserve Study:
Ecosystem Description. The Nature Conservancy,
Arlington, Virginia. pp.521-562.
Williams, B. 1989. The first breeding record of the Brown
Pelican in Virginia: A chronology. The Raven 60:1-3.
Williams, B. 2007. Summer records June-July 2007: Coastal
Region. Virginia Birds 4:7-8.
Williams, B. 2010. Summer records June-July 2010: Coastal
Region. Virginia Birds. 7:9-11.
Williams, B. 2011. Summer records June-July 2011: Coastal
Region. Virginia Birds 8(1):12-15.
Williams, B. 2012. Summer records June-July 2012: Coastal
Region. Virginia Birds 9(1):30-31.
Williams, B. 2013. Summer records June-July 2013: Coastal
Region. Virginia Birds 10(1):28-31.
Williams, B., R. A. Beck, B. Akers, and J. Via. 1990.
Longitudinal surveys of the beach nesting and colonial
waterbirds of the Virginia barrier islands. Virginia
Journal of Science 41:380-388.
Williams, B., B. Akers, R. Beck, J. Via, and S. Rottenborn.
1992. The 1991 Virginia barrier islands beach-nesting
and colonial waterbird survey. The Raven 63:96-101.
Williams, B., B. Akers, M. Beck, R. Beck, and J. Via. 2001.
The 2000 beach-nesting and colonial waterbirds survey
of the Virginia barrier islands. The Raven 72:132-136.
Williams, B., B. Akers, M. Beck, R. Beck, and J. Via. 2002.
A summary report of the 2001 Virginia barrier islands
beach-nesting and colonial waterbirds survey. The
Raven 73:10-16.
Williams, B., B. Akers, M. Beck, R. Beck, and J. Via. 2003.
A summary of the 2002 beach-nesting and colonial
waterbirds survey of the Virginia barrier islands. The
Raven 74:53-57.
Williams, B., B. Akers, M. Beck, R. Beck, and J. Via. 2006.
The 2005 beach-nesting and colonial waterbird survey
of the Virginia barrier islands. The Raven 77:27-33.
2014 Vol. 85(2)
THE RAVEN
Page 21
Table 1. Estimated number of breeding pairs for all geographic regions within the Coastal Plain of Virginia in 2013. The category
"colonies" refers to the number of colonies that included each species. "%Nests" is the portion of the population estimate that was
based on counts of nests rather than adults (see Methods).
Species
I
Colonies
I
Median
I
Range
I
%Nests
I
Pop. Est.
Waders
White Ibis 2
-----
13-356 3.5 369
Glossy Ibis 7 71 12-159 19.3 484
Great Blue Heron 258 12 2-1250 100 7809
Great Egret 43 38 1-300 79.5 2894
Snowy Egret 13 25 1-376 28.6 903
Tricolored Heron 10 19 1-266 14.2 718
Little Blue Heron 614 2-50 30.9 178
Cattle Egret 382-46 82.1 56
Green Heron 12 4 1-8 83.3 49
Black-crowned Night Heron 8 21 6-170 10.4 358
Yellow-crowned Night Heron 61 4 1-17 96.3 299
Gulls
Great Black-backed Gull 36 16 1-259 99.1 1172
Herring Gull 31 25 2-1100 98.9 3326
Laughing Gull 37 80 3-6400 >99.9 24160
Terns
Gull-billed Tern 917 2-120 100 294
Caspian Tern 2
-----
1-8 9
Royal Tern 8 16 1-5188 99.7 5321
Sandwich Tern 2
-----
5-23 11.1 28
Forster's Tern 57 17 3-642 98.8 2431
Common Tern 29 18 1-1158 100 1985
Least Tern 28 16 4-261 99.0 925
Others
Black Skimmer 19 30 2-307 93.4 1506
Double-crested Cormorant 9183 10-1109 100 2876
Brown Pelican 3348 36-1128 100 2454
Total
I
496
I
15
I
2-8600
I
94.5
I
60604
Page 22 Vol. 85(2)
THE RAVEN
2014
Table 2. Summary of species distributions across geographic areas within the Coastal Plain of Virginia in 2013. "Col"
=
the
number of colonies within the respective regions. "Prs"
=
the estimated number of breeding pairs within each region. "%"
=
the
percentage of the total population found within each region.
Seaside Bay Islands Urban Western Shore Southside
Species Col Prs
%
Col Prs
%
Col Prs
%
Col Prs
%
Col Prs
%
Waders
White Ibis 2 369 100.0
Glossy Ibis 4 384 79.3 3100 20.7
Great Blue Heron 1 52 0.7 25 311 4.0 14 640 8.2 33 6087 77.9 28 719 9.2
Great Egret 9692 23.9 5111 3.8 10 1061 36.7 12 551 19.0 7 479 16.6
Snowy Egret 7 755 83.6 5 115 12.7 1 33 3.7
Tricolored Heron 7 688 95.8 3 30 4.2
Little Blue Heron 4 150 84.3 2 28 15.7
Cattle Egret 248 85.7 1 8 14.3
Green Heron 7 23 46.9 5. 26 53.1
Black-crowned Night Heron 5277 77.4 381 22.6
Yellow-crowned Night Heron 1 2 0.7 39 3.0 57 288 96.3
Gulls
Great Black-backed Gull 20 868 74.1 15 298 25.4 160.5
Herring Gull 19 2945 88.5 11 338 10.2 1 43 1.3
Laughing Gull 30 21414 88.6 6 854 3.5 1 1892 7.8
Terns
Gull-billed Tern 8255 86.7 1 39 13.3
Caspian Tern 2 9 100.0
Royal Tern 4 62 1.2 3 71 1.3 1 5188 97.5
Sandwich Tern 1 517.9 0.0 1 23 82.1
Forster's Tern 45 1137 46.8 12 1294 53.2
Common Tern 22 694 35.0 6133 6.7 1 1158 58.3
Least Tern 25 533 57.6 3 392 42.4
Others
Black Skimmer 14 1135 75.4 4 156 10.4 1 215 14.3
Double-crested Cormorant 467 2.3 32369 82.4 1 257 8.9 1 183 6.4
Brown Pelican 3 597 24.3 31857 75.7
Total 135 33138 54.7 58 8163 13.5 81 11225 18.5 197 6880 11.4 29 1198 2.0
2014 Vol. 85(2)
THE RAVEN
Page 23
Table 3. Comparison of estimated number of breeding pairs in coastal Virginia for 1993,2003 and 2013. Percent change refers to
the population change between 1993and 2013.
Species
1993 2003
2013
I
0/0
Pop. Est. Pop. Est. Pop. Est. Change
Waders
White Ibis 3 77 369 +12200.0
Glossy Ibis 1008 818 484 -52.0
Great Blue Heron 9112 9136 7809 -14.3
Great Egret 2520 2720 2894 +14.8
Snowy Egret 2329 882 903 -61.2
Tricolored Heron 767 507 718 -6.4
Little Blue Heron 374 310 178 -52.4
Cattle Egret 1459 166 56 -96.2
Green Heron 154 60 49 -68.2
Black-crowned Night Heron 526 640 358 -31.9
Yellow-crowned Night Heron 388 241 299 -22.9
Gulls
Great Black-backed Gull 514 1084 1172 +128.0
Herring Gull 8801 4521 3326 -62.2
Laughing Gull 45387 44953 24160 -46.8
Terns
Gull-billed Tern 606 322 294 -51.5
Caspian Tern 8 1 9-12.5
Royal Tern 6250 2858 5321 -14.9
Sandwich Tern 30 7 28 -6.7
Forster's Tern 2939 2477 2431 -17.3
Common Tern 6781 1891 1985 -70.7
Least Tern 1171 843 925 -21.0
Others
Black Skimmer 3098 1828 1506 -51.4
Double-crested Cormorant 354 1338 2876 +712.4
Brown Pelican 368 1661 2454 +566.8
I
Total 94947 79343 60604 -36.2
2014 Vol. 85(2)
THE
RAVEN
Page 25
APPENDIX I: List of 24 colonial waterbird species surveyed in coastal Virginia, along with their A.O.U. alpha codes.
I
Species Alpha Code
I
Scientific Name
I
Great Black-backed Gull GBBG
Larus marinus
Herring Gull HERG
Larus argentatus
Laughing Gull LAGU
Larus airicilla
Gull-billed Tern GBTE
Sterna nilotica
Caspian Tern CATE
Sterna caspia
Royal Tern ROYT
Sterna maxima
Sandwich Tern SATE
Sterna sandvicensis
Forster's Tern FOTE
Sterna forsteri
Common Tern COTE
Sterna hirundo
Least Tern LETE
Sterna
aniillarum
Black Skimmer BLSK
Rynchops niger
Double-crested Cormorant DCCO
Phalacrocorax auritus
Brown Pelican BRPE
Pelecanus occidentalis
White Ibis WHIB
Eudocimus albus
Glossy Ibis GLIB
Plegadis falcinellus
Great Blue Heron GBHE
Ardea herodias
Great Egret GREG
Ardea alba
Snowy Egret SNEG
Egretta thula
Tricolored Heron TRHE
Egretta tricolor
Little Blue Heron LBHE
Egretta caerulea
Cattle Egret CAEG
Bubulcus ibis
Green Heron GRHE
Buiorides virescens
Black-crowned Night Heron BCNH
Nycticorax nycticorax
Yellow-crowned Night Heron YCNH
Nyctanassa violacea
... Following the 2003 survey a decision was made by the collective partners to reduce the survey interval to five years. Systematic surveys were conducted in 2008 (Watts and Paxton 2009) and 2013 (Watts and Paxton 2014). The 2018 survey represents a continuation of the series. ...
... The statewide population of great egrets in Virginia has increased three fold between 1993 and 2013 (Watts and Paxton 2014). This species has historically had a breeding distribution skewed to the coast. ...
... silversides, killifish, sandeels, bay anchovies) while diving and breed on barrier islands in the Eastern Shore of Virginia from late May to early July (Erwin 1977, Safina & Burger 1985. Common terns are listed globally as "least concern" by the IUCN Red List (International 2016), however the coastal Virginia population has declined 70.7% between 1993 and 2013 (Watts & Paxton 2014). This decline was mostly due to the invasion of laughing gulls within the Hampton Roads Tunnel Island, which was habitat for the largest common tern colony in Virginia and had compensated for common tern population numbers in the past (Watts & Paxton 2014). ...
... Common terns are listed globally as "least concern" by the IUCN Red List (International 2016), however the coastal Virginia population has declined 70.7% between 1993 and 2013 (Watts & Paxton 2014). This decline was mostly due to the invasion of laughing gulls within the Hampton Roads Tunnel Island, which was habitat for the largest common tern colony in Virginia and had compensated for common tern population numbers in the past (Watts & Paxton 2014). The common tern population in Maryland has also declined 86% since the early 1990s 5 . ...
Full-text available
Thesis
Due to increasing US interest in developing wind energy sites in offshore waters, we synthesized existing data on colonial breeding seabird populations with the potential risk of interacting with lease areas in the mid-Atlantic. Previous efforts by BOEM and NOAA have predicted avian density using at-sea survey data; we seek to complement this work by focusing specifically on birds during the critical and energetically demanding breeding life history stage. We combined colony size and location for each species along the mid-Atlantic coast with buffers around the colonies that correlate with the species’ foraging range. We integrated population size, vulnerability to offshore wind, and foraging areas to create a multi-species vulnerability model and overlaid this model onto current BOEM lease areas. Our model determined areas of high-predicted vulnerability in the northern and southern ends of the Eastern Shore of Virginia, southern to mid-areas of the New Jersey coastline, and western Long Island of New York. Out of the total study area, 31.73% of the high-predicted vulnerable areas overlapped with currently leased areas for offshore wind energy development. We also compared our model to NOAA’s predicted density models and found they could be used together to identify areas with both high predicted density and high vulnerability as they overlapped 38.54% in our study area. The differences between these two models also suggest that simply relying on predicted density as a metric for determining impacts may miss areas that are critical for breeding birds. We also collected GPS location data on common terns (Sterna hirundo) at Dawson Shoals, Virginia during their 2017 nesting season. We analyzed their movement and behavior in relation to offshore wind sites. We determined that common terns most often utilized an area roughly half the size of the suggested foraging range found in the literature, and that some traditional risk-models may be overestimating the potential impacts of offshore wind development on seabirds. Tracking data should be integrated into methods used to minimize seabird impacts while developing an offshore wind energy industry in the mid-Atlantic.
... Kelp Gulls, Larus domincanus) predators that prey on waterbirds and chicks [49,53] are common in potential coastal breeding habitats in temperate South America. Elsewhere, foxes have been shown to impart strong control over seabird colonies [54], and increases in gull and Bald Eagle populations are correlated with ongoing declines in skimmers and other colonial waterbirds breeding in Virginia, USA [55]. While nesting success for passerines is generally low in tropical forests [56], skimmers can benefit from nesting on river islands [57] and from multi-species defense provided by allies, including the Large-Billed Tern (Phaetusa simplex) and Yellow-Billed Tern (Sterna superciliaris) [29]. ...
Full-text available
Article
Seasonal flooding compels some birds that breed in aquatic habitats in Amazonia to undertake annual migrations, yet we know little about how the complex landscape of the Amazon region is used seasonally by these species. The possibility of trans-Andes migration for Amazonian breeding birds has largely been discounted given the high geographic barrier posed by the Andean Cordillera and the desert habitat along much of the Pacific Coast. Here we demonstrate a trans-Andes route for Black Skimmers (Rynchops niger cinerascens) breeding on the Manu River (in the lowlands of Manu National Park, Perú), as well as divergent movement patterns both regionally and across the continent. Of eight skimmers tracked with satellite telemetry, three provided data on their outbound migrations, with two crossing the high Peruvian Andes to the Pacific. A third traveled over 1800 km to the southeast before transmissions ended in eastern Paraguay. One of the two trans-Andean migrants demonstrated a full round-trip migration back to its tagging location after traveling down the Pacific Coast from latitude 9° South to latitude 37° S, spending the austral summer in the Gulf of Arauco, Chile. This is the first documentation of a trans-Andes migration observed for any bird breeding in lowland Amazonia. To our knowledge, this research also documents the first example of a tropical-breeding waterbird migrating out of the tropics to spend the non-breeding season in the temperate summer, this being the reverse pattern with respect to seasonality for austral migrants in general.
... Based on most recent censuses (Molina et al. 2010), the size of breeding populations within these states is fairly similar. In 2005, 252-257 breeding pairs were estimated to reside within California, whereas 293-311 breeding pairs were reported in Virginia in 2003 and 2008 (Watts and Paxton 2009;Molina et al. 2010). Thus, the qualitatively similar genetic diversity from these groups may reflect similar underlying local effective population sizes within these regions. ...
Full-text available
Article
Gull-billed Terns (Gelochelidon nilotica) are among the most widespread, yet scarce, Charadriiformes in the world. Two subspecies are recognized in the United States: G. n. aranea breeds along the U.S. Atlantic and Gulf coasts and G. n. vanrossemi breeds in the Salton Sea and San Diego Bay of California. Conservation concerns exist for the species due to its low abundance in the United States and apparent declines in some parts of its North American range. We used nuclear microsatellite markers and mitochondrial DNA sequences to assess genetic diversity and differentiation patterns among Gull-billed Tern populations from Virginia, Texas, and California. We also tested for evidence of population bottlenecks, and evaluated the support our data provide for the North American subspecies. Genetic diversity was highest in Texas and underscored the importance of habitat in that large population. Significant population differentiation existed, but could not be consistently identified using various analytical approaches and suggested that the magnitude of differentiation was low. No evidence for bottlenecks was identified. Our data could not distinguish individuals from different subspecies and therefore do not support the current intraspecific taxonomy. Tenable explanations for many findings are related to the low site tenacity demonstrated by the species.
Full-text available
Article
Coastal Louisiana—and its Mississippi River Delta, in particular—provides large and diverse habitats for many types of birds in North America and beyond. The Mississippi River and its distributaries have shaped Louisiana's unique coast, which includes extensive marsh and marsh islands, sandy barrier headlands and sandy islands, and isolated patches of maritime forest on natural levees, cheniers, and canal spoil banks. Louisiana thus supports large populations of many obligate marsh bird species as well as marine bird species that require islands for breeding sites. Here, we have collated available data and attempt to estimate the breeding population sizes of 17 bird species in coastal Louisiana. We then summarize the importance of the Louisiana coast for these bird species in the contexts of regional, national, and global bird populations. These preliminary estimates indicate that Louisiana's coast supports a high percentage of regional, national, and, in some cases, global populations of several coastal bird species. For example, we estimate that 73% of the United States population of Sandwich Tern (Thalasseus sandvicensis) breeds in Louisiana, and comparable estimates range from 24 to 55% for Mottled Duck (Anas fulvigula), Clapper Rail (Rallus crepitans), Tricolored Heron (Egretta tricolor), Wilson's Plover (Charadrius wilsonia), Royal Tern (Thalasseus maximus), Black Skimmer (Rynchops niger), and Seaside Sparrow (Ammodramus maritimus). Because most of these other bird species are distributed across state, regional, and national jurisdictions, management of birds and bird habitats in Louisiana has wide-reaching implications for the conservation of these shared natural resources. In this light, this paper is intended to be a resource for managers of avian resources in North America and beyond.
Full-text available
Article
Virginia supports a diverse community of breeding birds that has been the focus of investigation for more than 400 years. The avifauna reflects the latitudinal position of the state and the fact that the border extends from the Atlantic Ocean to the Appalachian Mountains. A total of 224 species have been recorded breeding in Virginia, 214 of which are extant. Twenty species have colonized the state since 1900 including 14 since 1950. Of all extant species, 102 (48%) are considered common at least somewhere in the state and 64 (30%) are rare to very rare. Diversity varies by physiographic region with 179 (83%), 168 (78%) and 141 (66%) in the Coastal Plain, Mountains and Piedmont, respectively. Two significant landscape features make significant contributions to the statewide diversity including tidal waters along the coast and isolated spruce-fir forests of the Appalachians that represent Pleistocene-era relicts. In all, nearly 25% of the statewide avifauna is either wholly or nearly confined to tidal water and 10% is confined to "sky island" refugia. Since 1978, 25 species of birds throughout Virginia have been identified as requiring immediate conservation action. A retrospective assessment shows that 5 of these species including osprey (Pandion haliaetus), bald eagle (Haliaeetus leucocephalus), peregrine falcon (Falco peregrinus), brown pelican (Pelecanus occidentalis) and piping plover (Charadrius melodus) have recovered to or beyond historic numbers. Three species including Bewick's wren (Thryomanes bewickii), Bachman's sparrow (Peucaea aestivalis) and upland sandpiper (Bartramia longicauda) have been lost from the state and the black rail (Laterallus jamaicensis), loggerhead shrike (Lanius ludovicianus) and Henslow's sparrow (Ammodramus henslowii) are in imminent danger of extirpation. Several species including the peregrine falcon, piping plover, Wilson's plover (Charadrius wilsonia) and red-cockaded woodpecker (Picoides borealis) are the focus of intensive monitoring and management programs. The underlying causes of imperilment remain unclear for several species of concern, limiting our ability to development effective conservation strategies.
Full-text available
Article
We conducted a systematic survey of colonial waterbirds in coastal Virginia during the breeding season of 2003. More than 800 surveys were conducted of 446 colonies during the breeding season of 2003. Colonies contained an estimated 79,343 breeding pairs of 24 species. Gulls were the most abundant group with more than 50,000 breeding pairs. Terns and waders accounted for 8,399 and 15,557 pairs respectively. Laughing gulls were several times more abundant than any other species and represented 56.7% of the total waterbird community. Great Blue Herons were the most widely distributed species with more than 200 colonies documented. The barrier island/lagoon system of the Eastern Shore was the most important region for the majority of colonial species encountered. This region supported 22 of the 24 species found in coastal Virginia and accounted for greater than 70% and 35% of all breeding pairs and colonies, respectively. For 18 of the 24 species, the region supported more than 50% of the known coastal population. The colonial waterbird community in coastal Virginia declined by more than 16% during the 10 years between 1993 and 2003. Losses were widespread with 17 of 24 species exhibiting negative trends. The magnitude of declines varied between species with 10 species declining by more than 40% and 4 species declining by more than 70%. Cattle Egrets showed the highest loss rate, declining from an estimated 1,459 to only 166 pairs over the 10-yr period. Seven species increased between 1993 and 2003. Dramatic expansions were documented for White Ibis, Great Black-backed Gull, Double-crested Cormorant, and Brown Pelican. The overall waterbird community declined within all geographic regions except the western shore. Due to the area’s importance to the overall community, declines on the seaside of the Delmarva Peninsula accounted for more than 85% of the broader coastal decline.