Tern Numbers Research Articles

Large nocturnal roosting aggregations and mass movements of Whiskered Terns in Liuwa Plain National Park, Zambia

The Whiskered Tern (Chlidonias hybrida) is little studied in southern Africa. In Zambia, it is primarily found in the south and west of the country, where the Barotse Floodplain and Kafue Flats are known to contain substantial numbers of terns. Although the species is common in Liuwa Plain National Park, there are no high counts. While in Liuwa in July 2021, we observed over 1,600 Whiskered Terns at a nocturnal roost, which was located on floating vegetation in the middle of a pan. In June 2022 we observed three large nocturnal roosts ranging from 400–725 terns as well as large early morning movements of as many as 850 terns dispersing towards floodplains outside Liuwa. Our observation in 2021 represents one of the highest concentrations of Whiskered Terns recorded in southern Africa and those in 2022 suggest terns may commute tens of kilometers to forage during the day but return to Liuwa to roost communally.

<i>Corrigendum to:</i> Distribution and foraging by non-breeding Caspian Terns on a large temperate estuary of south-western Australia – preliminary investigations

This study investigates the distribution, abundance, and foraging ecology of Caspian Terns, <i>Hydroprogne caspia</i>, during 5 months of their non-breeding season, in the Peel-Harvey Estuary, south-western Australia. Observations were carried out at 20 sites around the estuary and 6 main areas (13 sites) where terns were abundant. Terns were observed every hour over 5h time-blocks in the morning, midday, and afternoon, and the number of birds, number of birds foraging and time spent foraging were recorded for 10min on the hour. From the 760h of observation, a single overnight roosting site was identified in November, where a maximum of 147 birds were counted in February, after which time the roosting site appeared to shift. The total number of terns, foragers and proportion of time foraging varied amongst the six areas and foraging activity differed amongst times of day. Two areas, both characterised by large, sandy spits adjacent to shallow water, one adjacent to a river mouth and one near an ocean channel, were particularly important for terns and their foraging. Foraging activity was higher in the morning than at other times of day. Although salinity, air temperature, water temperature and wind speed were correlated with the total terns, foragers and proportion of time foraging, the correlations accounted for <25% of the total variation explained. The results of this study provide information for evaluating the use of Caspian Terns as bio-indicators of the Peel-Harvey Estuary and highlights the importance of this system during the non-breeding period.

Distribution and foraging by non-breeding Caspian Terns on a large temperate estuary of south-western Australia – preliminary investigations

This study investigates the distribution, abundance, and foraging ecology of Caspian Terns, Hydroprogne caspia, during 5 months of their non-breeding season, in the Peel-Harvey Estuary, south-western Australia. Observations were carried out at 20 sites around the estuary and 6 main areas (13 sites) where terns were abundant. Terns were observed every hour over 5 h time-blocks in the morning, midday, and afternoon, and the number of birds, number of birds foraging and time spent foraging were recorded for 10 min on the hour. From the 760 h of observation, a single overnight roosting site was identified in November, where a maximum of 147 birds were counted in February, after which time the roosting site appeared to shift. The total number of terns, foragers and proportion of time foraging varied amongst the six areas and foraging activity differed amongst times of day. Two areas, both characterised by large, sandy spits adjacent to shallow water, one adjacent to a river mouth and one near an ocean channel, were particularly important for terns and their foraging. Foraging activity was higher in the morning than at other times of day. Although salinity, air temperature, water temperature and wind speed were correlated with the total terns, foragers and proportion of time foraging, the correlations accounted for <25% of the total variation explained. The results of this study provide information for evaluating the use of Caspian Terns as bio-indicators of the Peel-Harvey Estuary and highlights the importance of this system during the non-breeding period.

Inuit knowledge of Arctic Terns (Sterna paradisaea) and perspectives on declining abundance in southeastern Hudson Bay, Canada.

The Arctic Tern (Sterna paradisaea; takatakiaq in Inuttitut) breeds in the circumpolar Arctic and undertakes the longest known annual migration. In recent decades, Arctic Tern populations have been declining in some parts of their range, and this has been a cause of concern for both wildlife managers and Indigenous harvesters. However, limited scientific information is available on Arctic Tern abundance and distribution, especially within its breeding range in remote areas of the circumpolar Arctic. Knowledge held by Inuit harvesters engaged in Arctic Tern egg picking can shed light on the ecology, regional abundance and distribution of this marine bird. We conducted individual interviews and a workshop involving 12 Inuit harvesters and elders from Kuujjuaraapik, Nunavik (northern Québec), Canada, to gather their knowledge of Arctic Tern cultural importance, ecology, and stewardship. Interview contributors reported a regional decline in Arctic Tern numbers which appeared in the early 2000s on nesting islands near Kuujjuaraapik. Six possible factors were identified: (1) local harvest through egg picking; (2) nest disturbance and predation; (3) abandonment of tern nesting areas (i.e., islands that have become connected to the mainland due to isostatic rebound); (4) climate change; (5) natural abundance cycles within the Arctic Tern population; and (6) decline of the capelin (Mallotus villosus) in the region. Recommendations from Inuit contributors related to Arctic Tern stewardship and protection included: (1) conduct more research; (2) let nature take its course; (3) conduct an awareness campaign; (4) implement an egg picking ban; (5) coordinate local egg harvest; (6) start 'tern farming'; (7) protect Arctic Terns across their migration route; and (8) harvest foxes predating on terns. Our study highlighted complementarities between Inuit knowledge and ecological science, and showed that Inuit harvesters can make substantial contributions to ongoing and future Arctic tern research and management initiatives.

Caspian Tern Response to Managed Reductions in Nesting Habitat

ABSTRACTPredation on smolts by Caspian terns (Hydroprogne caspia) has been identified as a factor limiting the restoration of some populations of anadromous salmonids (Oncorhynchus spp.) from the Columbia River basin that are listed under the U.S. Endangered Species Act. Implementation of a management plan to reduce numbers of Caspian terns nesting at the 2 largest colonies in the Columbia Plateau region of Oregon and Washington, USA, began in 2014 and is ongoing. We investigated the response of Caspian terns during 2014–2016 to reductions in nesting habitat at these 2 colonies. Management prevented terns from nesting at both colonies, and the estimated numbers of nesting pairs in the region declined significantly from a mean of 877 pairs during premanagement to 769 and 675 pairs in 2015 and 2016, respectively. The management objective of reducing numbers of nesting terns in the Columbia Plateau region to ≤200 breeding pairs was not achieved during the first 2 years of full implementation of the plan. Regional nesting success did not decline significantly following the initiation of management, and remained at levels considered sufficient to sustain the regional subpopulation. Despite the species’ capacity for long‐distance breeding dispersal, the majority of displaced terns exhibited stronger than expected philopatry to the Columbia Plateau region. Analysis of resightings of banded terns indicated that most (>80%) terns that nested in the Columbia Plateau region premanagement returned to the region in 2015 and 2016, but the proportion that returned as breeders decreased while the proportion that returned as nonbreeding floaters increased compared with premanagement. The proportion of banded terns that were unobserved also increased during management years, suggesting that more terns became floaters in the Pacific Flyway and went unobserved because they were prospecting and foraging in locations or regions where there was little or no monitoring. The unexpectedly high regional philopatry exhibited by terns during management was likely a reflection of the low availability of suitable alternative nesting habitat outside the region. Most terns that remained in the region displayed considerable flexibility in nest site selection by nesting either at a previously smaller, intermittently successful breeding colony or at a small new colony where nesting activity had not previously been recorded. As long‐lived seabirds, Caspian terns may integrate information regarding nesting success over several years before choosing to change nesting locations, longer than the 2 years of this study, especially if alternate locations are distant or intermittently available, or a history of nesting at multiple locations exists within the region. © 2020 The Wildlife Society.

Least Tern (Sternula antillarum) Population Response to Water Levels on Cheyenne River and Oahe Reservoir, South Dakota, USA

Consideration of annual population count data, stream flows, water levels, and nesting habitat availability over a 29-year period suggest that Least Terns (Sternula antillarum athalossos) nesting along the Cheyenne River and Oahe Reservoir in South Dakota, USA, select areas primarily in response to reservoir water levels early in the breeding season. Generalized linear models were selected in an information-theoretic framework and showed important relationships between adult Least Tern numbers and reservoir levels, as well as a negative long-term temporal trend in both survey areas. Reservoir levels alone could not account for the temporal trend. The number of adult Least Terns on the Cheyenne River was positively correlated (R = 0.668) with mean May reservoir water levels—a more important relationship than that between adult numbers and river levels. The number of adults on the Oahe Reservoir was negatively correlated (R = -0.573) with mean May reservoir water levels. Numbers of adults on the Cheyenne River and on Oahe Reservoir were negatively correlated (R = -0.684), suggesting that birds may interact as one population across the two areas. This information should help managers to consider ecological relationships among segments of the Least Tern population on the Missouri River and its tributaries and options for managing Least Terns on the Cheyenne River, Oahe Reservoir, and elsewhere on the Missouri River system.

Current distribution, abundance, and breeding biology of White Terns (Gygis alba) on Oahu, Hawaii

White terns (Gygis alba) are common on many islands in the tropical and subtropical Pacific, Atlantic, and Indian oceans, but in the southeastern Hawaiian Islands they are found only on Oahu, where they are listed as threatened by the State of Hawaii. In 2016, we censused the White Tern population on Oahu, mapped their distribution, and investigated their breeding biology. The total White Tern population on Oahu was 2,308 birds, including 1,408 breeders and ∼900 nonbreeders. The number of White Terns on Oahu has increased 282% since the previous census in 2002, for an average annual population growth rate of 7.7%. We observed White Terns only in urban and suburban areas of Honolulu and not in other parts of the island. Breeding occurred year-round, with 2 peaks in egg-laying in March and October. Hatching success was 69%, fledging success was 83%, and overall breeding success was 57%. Pairs made an average of 1.75 (SE 0.09) breeding attempts per year and produced an average of 1.08 (0.09) offspring per year (range 0–3). Terns used >58 tree species for breeding and roosting, most of which were large (>45 cm diameter). Average height in trees of breeding attempts was 9.1 (0.2) m. White Terns are thriving in urban Honolulu and are not seriously affected by numerous potential sources of human disturbance or predation from nonnative mammals, but some efforts will help to ensure their status remains secure. Received 7 July 2017. Accepted 6 January 2018.

Efficacy of decoys and familiar versus unfamiliar playback calls in attracting Common Terns to a rehabilitated wetland on Lake Ontario

Common Terns (Sterna hirundo) are colonial-nesting waterbirds that have experienced long-term population declines on the Great Lakes. Lack of nesting habitat, especially due to competition with Ring-billed Gulls (Larus delwarensis), is thought to be an important cause of this decline. Therefore, it is important to create and maintain good nesting habitats for Common Terns, as was done in Windermere Basin, a historically polluted wetland in Hamilton Harbour. It was extensively restored from 2010–2013, including the construction of three new habitat islands designed for Common Tern nesting. We used playback systems and decoys to attract Common Terns to the new islands in 2013 and assessed the effectiveness of three different call types: local colony sounds recorded in Hamilton Harbour, foreign calls recorded elsewhere in the Great Lakes, and on the Atlantic Coast of North America. These playback types were rotated through sound systems on the three new islands, and a control island had no equipment. Two-hundred and seventy-three pairs of Common Terns successfully nested in the new habitat, and 244 chicks were hatched. However, we did not find evidence that social attractants were effective. Furthermore, there was no significant difference in the effect of the Hamilton Harbour, Great Lakes and Atlantic Coast of North America playbacks on Common Tern numbers or nests, but there was a significant negative effect of Gull numbers on Tern numbers. Colonizing individual Terns likely had prior experience nesting in Windermere Basin, and took advantage of the newly available habitat. These early colonizers would have been more salient to other Terns than the social attractants used in our experiment. Gull numbers declined after we carried out several nest removals (under permit). Therefore, availability of good quality habitat, with Gull numbers controlled, appeared important in re-establishing colonies of Common Terns in the Great Lakes region. Further research is required on the efficacy of social attractants.

Black tern (Chlidonias niger) breeding site abandonment in U.S. Great Lakes coastal wetlands is predicted by historical abundance and patterns of emergent vegetation

Breeding colonies of black terns (Chlidonias niger) have become increasingly rare in U.S. Great Lakes coastal wetlands since the mid-twentieth century, with an almost 90% decline in the number of active colony sites since 1991. Although the specific causes of this wetland species’ decline are unknown, habitat loss and degradation are thought to be a major barrier to conservation. Using data from the Great Lakes Colonial Waterbird Survey, we took a unique regional and historical approach to investigate the relationship between black tern colony site abandonment and a suite of local and landscape-scale habitat features in U.S. Great Lakes coastal wetlands. We employed logistic regression models and a combination of stepwise selection procedures to identify the best predictive model for black tern colony abandonment. According to the selected model, breeding colonies with fewer nests were more likely to be abandoned over the following decadal observation period than breeding colonies with more nests. Colony sites were also more likely to be abandoned when vegetation within the wetland shifted towards larger, denser clusters. We performed a simulation study that showed that failing to account for association between observations from the same site affected model selection results, but that cross-validation error for the selected model remained low unless site effects were very strong. Results of this study suggest that focus on protection of sites harboring large numbers of black terns and vegetation management will help limit further colony abandonments.

Local Black TernChlidonias nigerPopulation Trends in Relation to Nest Platform Provisioning

The population of Black Terns in The Netherlands strongly declined in the period from 1950 to 1980. In recent years numbers have been more stable. The supply of artificial nest platforms has successfully attracted breeding Black Terns, and 80% now breed on platforms. In this paper we describe the development in numbers and breeding success of a Black Tern population in The Netherlands over the period 1982–2015, where ample nest platforms have been supplied over time. Using this database we question whether we can increase the breeding population by supplying platforms. We are uncertain whether tern numbers responded to an increase in nest platforms, or whether researchers responded to an increase in tern numbers by putting out more nest platforms. We analyse (1) settlement and breeding success in relation to nesting substrate, (2) the covariation between breeding numbers and platform numbers over time and space, and (3) the density dependence of settlement and breeding success. Against this background we analyse whether the annual change in platform numbers is followed by a change in tern numbers, as would be expected if there was a causal link between the two. We show that in our study area reproduction on artificial platforms was higher than on natural substrate and that the tern population in the whole study area increased over the study period. This increase in numbers was associated with an increase in the number of platforms, as expected when platforms affect tern numbers. Settlement in the first year after introduction of the platforms was higher, but in later years there was no correlation between annual change in the number of platforms and annual change in the number of breeding pairs. We did not detect a decline in the number of fledglings produced per pair with increasing tern breeding density. In conclusion, although the general pattern suggests positive effects of platform numbers on tern numbers, we are strictly speaking not able to show that supplying nest platforms caused the increase in the local Black Tern population over the study period. The answer awaits large scale experiments with control areas and individually marked birds to quantify survival and dispersal.

Numbers of Terns Breeding Inland in California: Trends or Tribulations?

Numbers of Terns Breeding Inland in California: Trends or Tribulations?

Population estimates of the breeding birds of the Tinhosas islands (Gulf of Guinea), the only major seabird colony of the eastern tropical Atlantic

The Tinhosas islands, in São Tomé e Príncipe, host the most important seabird breeding colony in the Gulf of Guinea, but information on its conservation status was hitherto unpublished or anecdotal, the last assessment having been performed in 1997. A two-day expedition to the Tinhosas islands was undertaken to estimate the status of breeding seabirds in 2013. Four of the five seabird species known to breed in São Tomé e Príncipe, namely Brown Booby Sula leucogaster, Sooty Tern Onychoprion fuscatus, Brown Noddy Anous stolidus and Black Noddy Anous minutus, occur on the Tinhosas. A decrease of 80% in Brown Booby numbers, possibly due to occasional exploitation, and a 30% increase in Sooty Tern and Black Noddy numbers, were found compared to 1997 data although survey methods differed. Breeding of Brown Noddy and Madeiran Storm-petrel Hydrobates castro remains unconfirmed. Our estimates confirmed that BirdLife International Important Bird and Biodiversity Area criteria are met for at least one species, the Sooty Tern. The islands are not legally protected, nonetheless, apart from moderate levels of disturbance by fishermen who land on Tinhosa Grande, no alien species were seen, and no immediate threats to the Tinhosas colony were detected. Multiple visits within and between years are recommended, to census breeders, monitor threats and establish breeding phenologies.

The Influence of Spring Flood Water Levels on the Distribution and Numbers of Terns (On the Example of the Lower Desna River)

The floodplain reservoirs of the lower Desna River are known to represent suitable breeding habitats for the Black Tern (Chlidonias niger) and the White-winged Tern (Chlidonias leucoptera), while the Common Tern (Sterna hirundo) and the Little Tern (Sterna albifrons) nest on sandy islands and river spits at the river bed. We combined analysis of Landsat 8 satellite images and the breeding abundance of the lower Desna River resident terns to investigate if the levels of the floodplain inundation affect the terns’ distribution and numbers. Under the high flood conditions of 2013, we observed a significant decrease in the numbers of colonies and nesting pairs of the Common and Little Terns, which was probably caused by the delayed exposure of their breeding habitats at the river bed. In contrast, in the low water conditions of 2014, areas of sandy islands and river spits increase in the form of temporary sandbanks. Under low-water conditions, we observed a marked increase of the number of colonies and nesting pairs of the Little Tern, while the White-winged Tern disappeared from nesting sites and the Black Tern decreased in numbers.

Assessing regional populations of ground-nesting marine birds in the Canadian High Arctic

The Queens Channel region of Nunavut is an ecologically distinct area within the Canadian High Arctic consisting of an extensive archipelago of small, low-lying gravel islands throughout which form several localized but highly productive polynyas. We used aerial survey and colony-monitoring data to assess regional- and colony-level fluctuations in the number of birds in this region between 2002 and 2013. Regional and colony-specific monitoring suggested that common eider ( Somateria mollissima ) numbers are increasing, while numbers of Arctic terns ( Sterna paradisaea ) may be in decline. Based on these data, we suggest that even infrequent comprehensive surveys are more useful than annual monitoring at specific sites in generating an accurate assessment of ground-nesting seabird populations at the regional level, and that dramatic fluctuations at individual colonies probably belie the overall stability of regional populations. Keywords: Ground-nesting; seabirds; High Arctic; Nunavut; common eider; Arctic tern. (Published: 7 April 2015) Citation: Polar Research 2015, 34 , 25055, http://dx.doi.org/10.3402/polar.v34.25055

The current state of populations of the common tern Sterna hirundo (Linnaeus, 1758) and the Kamchatka tern S. camtschatica (Pallas, 1811) in northern Sakhalin

This paper presents data on the numbers of nesting common and Kamchatka tern populations on the northeastern coast of Sakhalin Island over a more than 20-year period. Distribution maps of the main tern colonies (Chaika, Lyarvo, and Wrangel islands, and an unnamed island situated in Chaivo Bay) are given. Taking into account the current data concerning southern Sakhalin colonies, the total number of terns in Sakhalin Island is about 9000 pairs for the Kamchatka tern and up to 16000 pairs for the common tern. The main biotic and abiotic factors that determine the population dynamics and distribution of nesting terns in northern Sakhalin Island are enumerated.

The Use of Avian Resources by the Forgotten Slaves of Tromelin Island (Indian Ocean)

ABSTRACTOn 31 July 1761, the Utile, a French slave ship from the Compagnie française des Indes, illegally loaded with Malagasy slaves, was shipwrecked on the desert islet of Tromelin. Two months after the disaster, the French crew left the island on a boat constructed from the wreckage and abandoned the slaves. Fifteen years later, Chevalier de Tromelin rescued eight survivors. An archaeological excavation recently conducted by M. Guérout and T. Romon revealed how the forgotten slaves adapted themselves to this hostile environment. The Malagasy survived using natural resources of the islet and material from the Utile. This paper, based on the archaeozoological analysis of almost 18 000 bird bones, focuses on their use of avian resources. The Malagasy survivors captured numerous individuals from a breeding colony of sooty tern Onychoprion fuscatus, as indicated by the presence of medullary bone and immature birds. Cut marks and localised burning at the bone extremities testify to the cooking method used. Under‐representation of the bones from the distal extremity of the wing, together with the rare written archives collected after the rescue, give evidence of the utilisation of feathers as raw material. An estimate of the total number of terns and eggs that were collected, compared with historical and modern ornithological observations, allows us to discuss the consequences of human predation on the disappearance of the sooty tern colony from Tromelin Island. Copyright © 2013 John Wiley & Sons, Ltd.

Diversity and abundance of water birds in a subarctic lake during three decades

The numbers of divers, ducks, gulls, terns and waders in the 15 km2 oligotrophic lake Takvatn, North Norway were estimated six times during 1983-2012. Systematic mapping surveys were done by boat within the first week after ice-break in June. Twenty-one species were observed over the years and 12 were regarded as breeding on the lake. Red-breasted merganser Mergus serrator was the dominant diving bird, with estimated minimum number of pairs varying from 15 to 39 among years. Black-throated diver Gavia arctica (1-3 pairs), tufted duck Aythya fuligula (2-15 pairs) and common scoter Melanitta nigra (1-5 pairs) bred regularly, while velvet scoter Melanitta fusca (1-2) and goldeneye Bucephala clangula (2-4) were found in some years and mallard Anas platyrhynchos (1 pair) and wigeon Anas penelope (1 pair) in one year. Common gull Larus canus (6-30 pairs) and arctic tern Sterna paradisaea (2-35 pairs) bred in all years. Common sandpiper Tringa hypoleucos (3-9 pairs) and redshank Tringa totanus (1-4 pairs) were regular waders. Density variations of mergansers, gulls and terns are possibly related to density variations of three-spined sticklebacks Gasterosteus aculeatus, their dominant fish prey. The water birds are important links in the food web of the lake.

Potential Effects of Management on Caspian Tern Hydroprogne caspia Predation on Juvenile Salmonids at a Colony in San Francisco Bay, California

AbstractSan Francisco Bay is a proposed relocation site for some of the Caspian terns Hydroprogne caspia currently nesting at the world's largest colony for the species in the Columbia River estuary and consuming salmonids listed under the U.S. Endangered Species Act (ESA). However, several runs of salmonids listed under the ESA occur in San Francisco Bay and managers are concerned that increased Caspian tern predation may pose a threat to the recovery of these fish. We used a bioenergetics modeling approach, employing estimates of tern energy requirements and proportions of energy supplied by various prey types, to estimate the consumption of juvenile salmonids by Caspian terns nesting on Brooks Island in central San Francisco Bay during 2008 and 2009. Estimated salmonid consumption was ∼205,000 smolts (95% confidence interval, 175,000–245,000 smolts) in 2008 and ∼167,000 smolts (144,000–191,000 smolts) in 2009. The interannual difference in smolt consumption was due to the smaller size of the tern colony and lower nesting success in 2009. Estimated predation rates on ESA‐listed Central Valley spring‐run Chinook salmon Oncorhynchus tshawytscha (0.1%) were lower than those on unlisted fall‐run Chinook salmon (1.0%). Continuation of the current downward trend in the number of Caspian terns nesting on Brooks Island and the resulting reductions in salmonid predation would not be sufficient to reverse salmonid declines in San Francisco Bay. The proposed enhancement of the Brooks Island Caspian tern colony to 3,000 individuals would at most cause declines in annual population growth rates of 0.28% for fall‐run Chinook salmon and 0.02% for threatened spring‐run Chinook salmon, assuming that the mortality from tern predation is 100% additive.

Current Status and Abundance Trends of Common Terns Breeding at Known Coastal and Inland Nesting Regions in Canada

The status of Common Terns (Sterna hirundo) breeding in Canada is presented, with abundance trends in regions where data allow. Large (>12,000 pairs) concentrations of Common Terns nested in coastal Newfoundland, long the Gulf of St. Lawrence coast of New Brunswick, and in lakes Winnipeg, Winnipegosis and Manitoba in Manitoba. Nest numbers increased in the four provinces of Atlantic Canada ( 31%; 1973–2010), the Mingan Archipelago National Park Reserve Canada (MANPRC) in the Gulf of St. Lawrence ( 81%; 1986–2009) and possibly in Great Slave Lake ( 10%; 1988–2010). Nest numbers declined (-41%; 1976–2009) in Canadian waters of the North American Great Lakes. Based on recent census data (1999–2010), the number of Common Terns breeding in Canada was estimated at between 82,000–89,500 pairs, with possibly thousands of additional pairs elsewhere in Canada that have never been systematically censused: Manitoba, Saskatchewan, Alberta inland areas of eastern provinces and the boreal forest. Recommendations are that Common Terns be censused in these areas with protocols established for the Great Lakes and annual management be implemented at sites on the Great Lakes earlier identified as “high priority”. Adoption of these recommendations would achieve better understanding of national abundance trends and inform future consevation initiatives.

Population Decline of Black Terns in Wisconsin: A 30-Year Perspective

Abstract. Point-count surveys of Black Terns (Chlidonias niger surinamensis) were conducted in Wisconsin from 1980 to 2011 to assess statewide population trends of this declining species. The survey program consisted of 19 roadside transects, each with 15 stops (N = 285 stops total), spread across 15 counties throughout the state. Surveys were conducted at the same sites each year during three periods (1980–1982, 1995–1997, 2009–2011) by observers who visited each site once during the breeding season (25 May to 24 June) and counted the number of Black Terns seen during a 5-min interval. Over the three survey periods, statistically significant changes in abundance occurred on 14 of the 19 transects, most of which either were linear or exponential declines; no significant increases were evident. Survey-wide, the population declined in abundance by nearly 70% over the past 30 years and site occupancy declined by a similar percentage. Complete extirpation was recorded on four transects. Nest counts in two int...