Massachusetts Tern Inventory 1998

Bradford G. Blodget, State Ornithologist

Compiled results from our cooperator network indicate 1998 was, overall, another excellent year for terns in Massachusetts, with improvements in numbers and generally good to excellent productivity. A variety of factors contributed to these results, including improved site management practices, improved habitat conditions, abundant food supplies, and low predation problems at most sites. Despite a very wet May and June, there were no devastating storms and weather was not a limiting factor in 1998.

Census of terns in Massachusetts is accomplished using "pairs" as the basic census unit. Generally, complete nest counts are made, at some sites corrected using the Lincoln Index. At a few sites, pair estimates may be extrapolations based on partial nest counts or adult estimates adjusted for pairs by multiplying by 0.8. Where nest counts are made, the number of nests is converted to pairs on a 1:1 ratio. Estimates of the numbers of pairs reported and discussed in this summary, unless otherwise noted, are "A-period" estimates made during a standard 5-20 June window. "B-period" estimates, as sometimes referenced herein, are estimates made later than the "A-period" counts and are not included in the total pair estimates for the state.

During the 1998 season, nesting terns were located at 73 sites out of approximately 112 sites along the Massachusetts coastline where nesting has been recorded since careful record keeping began in 1970.

The biggest story in 1998 (if not for the decade) was the continued strong resurgence in common tern numbers, extending the strong rising trend evident since 1992. Also during 1998, roseate tern numbers made a nearly complete recovery from depressed year earlier levels and least terns continued at historically high levels. Both quantitative and qualitative assessments indicated that 1998 was, generally, another exceptionally strong year for productivity. Recent years of good production support a forecast for continued population growth over the next 3-4 years.

The U.S. Fish & Wildlife Service's Avian Diversity Program at Monomoy National Wildlife Refuge (Monomoy-South, Chatham) entered its third year in 1998 and handed in solid 2

results. Year-over-year estimates for common terns nearly quadrupled to 2,363 pairs compared to 641 in 1997. Especially gratifying were 22 pairs of roseate terns that were joined by at least 20 more pairs in the "B-period". Productivity was excellent. This colony is now second in size in the state by a good margin.

After years of discussion, MassWildlife initiated restoration efforts at Penikese Island, Gosnold. Common terns there increased to 137 pairs in 1998 compared to 29 pairs a year earlier. Productivity was excellent. Penikese Island, historically the largest (~10,000 pairs) ternery in Buzzards Bay into the 1950's, is viewed as a strategically important site for long-term securance of common and roseate tern populations in the state.

Common Tern

Common tern numbers moved strongly ahead for the sixth consecutive year, increasing 10% over the 1997 level to 13,214 pairs, a new "modern" high since careful record keeping began in 1970. Further consolidation into fewer larger colonies was evident in 1998. Sites with reported nesting activity fell to 28 vs. 36 a year earlier. Some 93% of all pairs were contained in the 5 largest colonies vs. 88% in 1997.

Driving growth in 1998 were year-over-year increases of 269% at Monomoy-South, Chatham (2,363 vs. 641 pairs) and 41% at Ram Island, Mattapoisett (1,307 vs. 930 pairs) that far offset modest declines at other sites. A "new" colony was discovered at "Central Square Piers, East Boston", where 40 pairs were discovered nesting on an old pier structure.

The 5 largest colonies in 1998, all containing >1,000 pairs, were: Plymouth Beach, Plymouth (4,948), Monomoy-South, Chatham (2,363), Bird Island, Marion (1,903), Nauset-New Island, Orleans (1,766) and Ram Island, Mattapoisett (1,307). Four additional colonies 100 pairs included Haystack Point, Edgartown (260 pairs), Penikese Island, Gosnold (137 pairs), Woodbridge Island, Newburyport (128 pairs) and Gray's Beach, Yarmouth (117 pairs).

Least Tern

The estimated least tern population remained in record territory above the 3,000 pair level in 1998. Estimated numbers fell 3% from 3,197 in 1997 to 3,085 pairs in 1998. However, on account of "A-period" colonies at Monomoy-South, Chatham and Nauset-Chatham that were unstable due to predation and thus may have been underestimated, coupled with difficulties in estimating the very large colony at Dunbar Point, Barnstable, this year's estimate is likely conservative.

The large colony that grew through the 1990's at Great Point, Nantucket, cresting the 1,000 pair mark in 1996 and peaking at 1,152 pairs in 1997, did not develop in 1998. Alternatively, birds appeared to be dispersed among a number of different sites offering good 3

habitat conditions during the "A-period". A number of these "A-period" colonies---notably Nauset-Chatham (253 pairs) and Monomoy-South, Chatham (246 pairs)---failed due to predation and probably contributed birds to Smith Point, Nantucket, where a rather unusually large (800 pairs) and productive "B-period" colony developed.

The largest "A-period" count was Dunbar Point, Barnstable, where 808 pairs were conservatively estimated on fresh dredged spoil, up from 28 pairs there in 1997. Nine other sites reported "A-period" estimates 100 pairs, including Nauset-Chatham (253), Monomoy-South, Chatham (246), Tern Island, Chatham (140), High Head, Truro (137), Gray's Beach, Yarmouth (124), Plymouth Beach, Plymouth (120), Quidnet, Nantucket (119), Tom Never's Head, Nantucket (111) and Eastville Beach, Oak Bluffs (100). Additional "B-period" estimates 100 pairs included Crane Beach, Ipswich (102) and, as discussed above, Smith Point, Nantucket (800).

There were 2 "new" sites where nesting least terns were reported for the first time since 1970, including Eel Point, Nantucket with 4 pairs (31 in the "B-period") and at French Watering Hole, Naushon Island, Gosnold with 2 pairs. Least terns nested at 57 sites in 1998, up from 49 a year earlier and 42 in 1996.

Roseate Tern

Roseate terns recovered from their depressed year-earlier levels, increasing 16% to 1,693 pairs, just short of the 1,743 pairs estimated in 1996. Birds returned to Ram Island, from which large numbers had departed in 1997 due to owl predation. Numbers there more than doubled to 543 pairs from 253 pairs a year earlier. Numbers at Bird Island were essentially stable, declining slightly from 1,179 pairs in 1997 to 1,113 pairs this year.

Small numbers of nesting roseate terns were embedded within common tern colonies at Monomoy-South, Chatham (22 pairs, with an additional 20+ pairs appearing in the "B-period"), Plymouth Beach (12) and at Nauset-New Island, Orleans (3). At Penikese Island, Gosnold, where a roseate tern restoration effort began in 1998, prospecting roseate terns were observed, but no actual nesting occurred. The continuing increase in common tern numbers and efforts to establish new productive colonies should foster an improved outlook for the endangered roseate tern.

Other Species

ARCTIC TERN numbers, boosted by the discovery of 6 pairs nesting with common terns at Penikese Island, rose from 5 pairs in 1997 to 12 pairs in 1998. This marked the first 4

double digit estimate for the state since 11 were reported in 1991. Unfortunately, despite excellent hatching success, none of the Penikese Arctic tern chicks is believed to have survived beyond 5 days of age. This was surprising, particularly in light of the fact that the common terns at the same site were highly productive. Elsewhere, Arctic terns were discovered nesting at Plymouth Beach (4 pairs) and at Nauset-New Island, Orleans (2 pairs). For the second year in a row, a pair of FORSTER' S TERNS joined nesting common terns in the great salt marshes of Plum Island Sound. A nest containing 1 egg was found on 23 June. This is currently the northernmost breeding location for this species on the Atlantic Coast.

BLACK SKIMMERS nested successfully at 2 sites in 1998. There were 4 pairs accounted for statewide in 1998 vs. 5 last year. Three pairs at Monomoy-South, Chatham collectively fledged 8 chicks. A late-nesting pair at Plymouth Beach hatched eggs on 1 September and fledged 2 young. LAUGHING GULL numbers were off 9% in 1998 with 709 pairs estimated vs. 781 a year earlier. Nesting occurred at the same two sites as in 1997, with 498 pairs at the headquarters Nauset-New Island, Orleans colony and 211 pairs at Plymouth Beach.

I extend my appreciation and thanks to all the agencies and individuals in the reporting network that make these detailed annual summaries possible. Data collected each season contribute to the historical and scientific record and are incorporated into the Division of Fisheries and Wildlife's Natural Heritage Database. It is through this database that records translate into real environmental action by provisions of the Massachusetts Wetlands Protection Act (MGL, Ch. 131, Sect. 40A) and the Massachusetts Endangered Species Act (MGL, Ch. 131 A).

Report prepared by BRADFORD G. BLODGET, State Ornithologist, MassWildlife, Field Headquarters, Route 135, Westborough, MA 01581-3337.Tele: (508) 792-7270 x152. Fax: (508) 792-7275. 12/1/98.

Table 1. RESULTS OF THE 1998 MASSACHUSETTS TERN INVENTORY. All results expressed in pairs. Data are collected for all species for the period 5-20 June. Colony numbers follow or are adapted from Erwin and Korschgen (1979). Numbers in parentheses reflect numbers of pairs recorded outside the census period ("B-counts") and are not included in the total pairs. Shaded sites either were not checked or were checked and no activity was detected in 1998. COLONY NUMBER COLONY NAME, TOWN ROST COTE ARTE LETE BLSK LAGU

324000 Miscellaneous sites, map 3241 324007 Woodbridge I., Newburyport 128 324007.1 Blackwater River Group, Salisbury2 324007.2 Chaces I., Newbury1 324008 Plum I. River Group, Newbury 51 (marshes-incl. Pine I., Little Pine I. and Jericho Creek)3 324009 Parker River Group (marshes) 13 324009.1 Plum I. Beach, Newbury-Rowley-Ipswich 22 324010 Roger I., Ipswich2 324010.2 Bagwell I., Ipswich 7 324010.3 Rowley Salt Marshes 6 324010.4 Lords I., Ipswich 4 324010.5 Ipswich Salt Marshes 2 324011 Crane Beach, Ipswich 1 61(102) 324038 Tinker's I., Salem 14 324038.1 Saugus River Bridge, Lynn-Revere 43 324040.3 Belle Isle Marsh, Boston1 6