Large Seabird Colonies Research Articles

Ecological niche overlap in the Arctic vegetation influenced by seabirds

In the High Arctic, nutrients are the most limiting resources, so terrestrial vegetation is of low complexity and grows slowly. However, locally, large seabird colonies increase soil fertility by deposition of faeces, supporting the development of rich and fast-growing plant communities. Here, we assessed how seabird colonies affected ecological niche segregation of plants, across the fertilisation gradient. Study sites were located near five little auk colonies, distributed longitudinally across the Svalbard archipelago. We described vascular plant composition and identified 13 environmental variables, based on which, we calculated and tested the niche overlap (NO) between the 18 most frequent species. Based on the hierarchical classification of the NO matrix, we distinguished typical High Arctic Vegetation (HAV), and Bird-Cliff Vegetation (BCV). The BCV was characterised by higher average NO and soil δ15N compared to HAV. The highest NO values across the fertilisation gradient were found on the border between the distinguished communities and were positively correlated with species diversity. We suggest that in the High Arctic, seabirds-delivered nutrients lead to the development of separate plant communities through the mechanism of avoiding inter-species competition, while simultaneous high species diversity and NO are related to high facilitation between plants on the border between the communities.

Trophic connectivity between the terrestrial and marine ecosystems of Malpelo Island, Colombia, evaluated through stable isotope analysis

The trophic dynamics of islands with low terrestrial primary productivity often depend on marine allochthonous inputs from nearby donor habitats. For instance, on Malpelo Island, Colombia (4° 00′ 05.63″ N; 81° 36′ 36.41″ W), the Nazca booby Sula granti affects the productivity and trophic dynamics of the terrestrial ecosystem by delivering nutrients, primary in the form guano, chick carcasses, and eggs. This study evaluated the trophic connectivity between the terrestrial and marine ecosystems of Malpelo Island, Colombia based on the isotopic (δ13C and δ15N) assessment of 403 samples (107 terrestrial and 296 marine) collected between 2017 and 2021. Isospaces were estimated based on δ13C and δ15N values, contribution of terrestrial sources in consumer diets (mixing model), 15 N enrichment in C3 plants, and interactions among environments (overlap). δ13C and δ15N values showed a larger terrestrial isospace (134.7‰2) than the marine isospace (117.2‰2). The mixing model indicated that detritusTerrestrial (median: 30.2%) contributed more to the food web than C3 plants (0.2%), reflecting high δ13CMarine content. The high isotopic overlap (> 60%) between terrestrial and marine isospaces suggests a significant trophic connection between environments. These results show the role of the marine ecosystem on the terrestrial ecosystem and the importance of S. granti regarding nutrient transfer between environments. The conservation of this seabird is essential to maintain the balance of this insular ecosystem. Using stable isotopes, this study was able to reveal trophic relationships between ecosystems associated with small oceanic islands that host large seabird colonies but have low primary productivity.

Морские птицы острова Тайночин (залив Шелихова, Охотское море)

The north of the Sea of Okhotsk is one of the least studied areas in Russia's Far East. Tainochin Island (61°48'35"N 159°19'35"E) in the north of Shelikhov Bay, despite its small size, supports a very large seabird colony of seabirds. The first and the only survey of seabird colonies on the island was held back in 1994. In 2017 more than 1000 digital images of colonies were made during a single- day survey (7.06.2017). We used these digital photographs to count seabirds on the island in order to compare the current species composition and numbers with historical data. In 2017, the numerous species were the Common Murre and the Thick-billed Murre (more than 45.5 thousand individuals, two species combined), the Black-legged Kittiwake (more than 13.5 thousand individuals), and the Slaty-backed Gull (more than 1.5 thousand individuals). Common species included the Tufted Puffin (324 individuals) and the Pelagic Cormorant (280 individuals). Rare species embraced the Spectacled Guillemot (13 individuals) and the Horned Puffin (7 individuals). The Parakeet Auklet, observed in small numbers in 1994, was not recorded in 2017. The numbers of the Tufted Puffin may be underestimated, assumingly making about 1.5-2 thousand individuals. The total number of breeding seabirds (more than 61 thousand individuals) might have been stable for decades, despite the relative accessibility of the island to humans. The Common Murre population has slightly declined (from 47K to 44K individuals), presumably due to regular egg harvesting. Simultaneously, there has been an increase in the number of Slaty-backed Gulls and Pelagic Cormorants.

Century-long stomatal density record of the nitrophyte, Rubus spectabilis L., from the Pacific Northwest indicates no effect of changing atmospheric carbon dioxide but a strong response to nutrient subsidy.

Triangle Island on Canada's Pacific coast is home to a large, globally important seabird breeding colony. The shrub Salmonberry Rubus spectabilis and tussock‐forming Tufted Hairgrass Deschampsia cespitosa together form ~70% of vegetation coverage and contain the vast majority (~90%) of seabird nesting burrows. Salmonberry has in recent decades greatly expanded its coverage, while that of Tufted Hairgrass has receded. Seabirds prefer not to burrow under Salmonberry, making its ongoing expansion a potential conservation issue. We investigated three hypotheses proposed to explain Salmonberry's expansion (climate change, biopedturbation, and nutrient input), using comparisons of stomatal density of Salmonberry leaves sampled from Triangle Island, other seabird colonies, other coastal locations, and from historical specimens in herbaria. Stomatal density helps regulate photosynthetic gain and control water loss, and responds to light, nutrient, carbon dioxide, and water availability. Differing patterns of stomatal density are expected among sample locations depending on which of the hypothesized factors most strongly affects Salmonberry's performance. Our data are most consistent with the nutrient input hypothesis. We discuss possible reasons why Salmonberry has expanded so recently, even though Triangle has been a large seabird colony for at least a century and likely much longer.

Ornithogenic vegetation: How significant has the seabird influence been on the Aleutian Island vegetation during the Holocene?

In the Aleutian Islands during the Holocene, terrestrial predators were actually absent; as a result, large seabird colonies thrived along the coasts or across entire islands. Bird guano enriches the soil with nitrogen, which can lead to the formation of highly modified ornithogenic (bird‐formed) ecosystems. For a more detailed investigation of avian influence, we reconstructed more than 10,000‐year‐old vegetation dynamics of the coast of Shemya Island (Near Islands) by pollen analysis. At the initial stages of vegetation development (10,000–4,600 cal year BP), sedge–heather tundra grew in the studied area. A seabird colony existed on Shemya from 4,600 to 2,400 cal year BP according to stable isotope analysis. During a period of at least 2,200 years, nitrogen enrichment led to the development of ornithogenic herb meadows with a high presence of Apiaceae. A long‐term increase in δ15N above 9–10‰ led to radical shifts in vegetation. Noticeable reduction of seabird colonies due to human hunting led to grass‐meadows spreading. After a prolonged decrease δ15N below 9–10‰ (2,400 cal year BP to present), there was a shift toward less productive sedge‐tundra communities. However, the significant enrichment of guano affected only the coastal vegetation and did not alter the inland Shemya Island.

Correction to: Categorizing the influences of two large seabird colonies on island freshwater ecosystems in the Northwest Atlantic Ocean

Due to an unfortunate mistake during the production process, the inset map in Fig. 1a is missing. The original article has been corrected and the correct display of Fig. 1 is also published here.

Categorizing the influences of two large seabird colonies on island freshwater ecosystems in the Northwest Atlantic Ocean

Seabird colonies influence ecosystems by releasing high concentrations of nutrients, metals, and contaminants via their wastes. Here, we examined seven lentic waterbodies impacted by two major colonies of Leach’s Storm-petrel (Hydrobates leucorhous), six from Baccalieu Island, Newfoundland and Labrador with ~ 1.95 million breeding pairs, and another from Grand Colombier Island, St. Pierre and Miquelon with ~ 200,000 breeding pairs. In comparison to nearby study sites not influenced by seabirds, we recorded more acidic pH, elevated specific conductance, and higher concentrations of dissolved organic carbon, total nitrogen, and total phosphorus in the seabird-influenced sites. The storm-petrels also significantly increased the metal concentrations of Co, Cu, Fe, Li, Nb, Ni, Sn, Sr, and Ti relative to reference sites. In the most highly affected ponds, the concentrations of Cd, Cu, and Fe exceeded Canadian Water Quality Guidelines for the Protection of Aquatic Life, implicating seabirds as biovectors of environmental contamination. Together, our data highlight the importance of seabirds, and likely other colonial organisms, as influential vectors that can strongly impact aquatic ecosystem chemistry and biota.

An ∼1100 yr record of human and seabird occupation in the High Arctic inferred from pond sediments

Abstract Seabirds in the Canadian Arctic congregate in large colonies, producing oases of biological productivity and diversity in coastal regions. Here, we examined sterols, stanols, and stable isotopes (δ15N and δ13C) in three 14C-dated pond sediment cores near a large seabird colony and archaeological site on Devon Island (Nunavut, Canada), showing historical occupation by the seabirds and an ancient human (Thule or Norse) settlement over an ∼1100 yr time period. Coprostanol in the sediment records captures the presence of humans at ca. 1150 CE, followed by their abandonment of the site by ca. 1300 CE. Increased seabird presence at this site after ca.1200 CE is indicated by increases in δ15N and cholesterol/sitosterol. Seabird population expansion is observed after ca. 1600 CE in δ15N and cholesterol/sitosterol profiles, coinciding with European whaling activities that expanded in the seventeenth through nineteenth centuries. Our study provides insights into human and seabird occupation in the High Arctic to inform archaeological and conservation efforts.

Northern gannets (Morus bassanus) are strongly affected by operating offshore wind farms during the breeding season

Northern gannets (Morus bassanus) have been ranked as one of the most vulnerable species in terms of collision with offshore wind farm (OWF) turbines, and strong avoidance of OWFs has been documented for this species. Gannets increasingly encounter OWFs within the ranges of their largest breeding colonies along the European coasts. However, information on their actual reactions to OWFs during the breeding season is lacking. We investigated the possible effects of OWFs located 23–35 km north of the colony on Helgoland in the southern North Sea on breeding gannets. GPS tags were applied to 28 adult gannets breeding on Helgoland for several weeks over 2 years. Most gannets (89%) predominantly avoided the OWFs in both years, but 11% frequently entered them when foraging or commuting between the colony and foraging areas. Flight heights inside the OWFs were close to the rotor-blade zone, especially for individuals predominantly avoiding the OWFs. Gannets preferred distances of 250–450 m to the turbines when being inside the OWF. A point process modelling approach revealed that the gannets resource selection of the OWF area compared with the surroundings (outside OWF = up to 15 km from the OWF border) was reduced by 21% in 2015 and 37% in 2016. This study provides the first detailed characterisation of individual reactions of gannets to OWFs during the breeding season and one of the first comprehensive studies of OWF effects on this species based on telemetry data. The documented effects need to be considered during the planning processes for future OWFs, especially those located close to large seabird breeding colonies.

Specific Features of Island Soil Formation (by the Example of Islands of the Northwest Pacific)

Soils of the Northwest Pacific, differing from continental soils, have been characterized on the basis of published data. It has been revealed that the climatic factor plays a great role in their formation. This is related to the precipitation amount, regime, and intensity, as well as to heat supply determined not only by insolation, but also by the wind regime and the presence of warm and cold currents. In addition, there is also an impulverization transportation of sea water salts with liquid precipitation. The distance from the continent and the size of islands determine the effect of these factors. The ornithogenic factor related to numerous large seabird colonies plays a particular role. All this determines the specificity of soil formation on the islands.

Recycled insular phosphates and coated grains: Case study from Little Cayman, British West Indies

AbstractPhosphatic limestones on the west end of Little Cayman, at an elevation of 3 to 4 m above sea level and ca 320 to 550 m inland of the coast, lie on top of a phytokarst surface that defines the upper boundary of the Pedro Castle Formation (Pliocene). These phosphatic limestones are formed of phosphatic lithoclasts, detrital phosphate grains, coated grains (glaebules), composite coated grains, biofragments and phosphate rafts that are held in a matrix that is formed of micrite, calcite cement, and non‐crystalline masses formed of P, Al, Si and Fe. The phosphate in these limestones is primarily hydroxylapatite, whereas the overlying soils, found in some areas, are formed of hydroxylapatite, crandallite and minor amounts of boehemite, kaolinite and quartz. Textures in the lithoclasts and detrital phosphate grains indicate that they were derived from older insular phosphates that that were largely removed by mining in 1890 to 1895. The coated grains (glaebules) typically have nuclei formed of a detrital phosphate grains that are encased by non‐crystalline cortical laminae that are composed primarily of Al with their variable red colour reflecting the variable Fe content. The phosphatic limestones developed in a low‐lying coastal area where the guano produced by a large seabird colony that was close to or mixed with terra rossa and marine carbonates that were washed onshore during storms/hurricanes. The Al, Fe, Si and rare earth elements found in the phosphatic limestones came from the terra rossa. Critically, this study documents the complex depositional regimes and diagenetic processes that can exist at the interface of marine carbonates, coastal phosphates and terrestrial soils as sea‐level fluctuations control phases of sediment accumulation that were periodically interrupted by periods of non‐deposition.

Within-colony spatial segregation leads to foraging behaviour variation in a seabird

Central-place foraging in large seabird colonies leads to high levels of intra-specific competition for food resources, often resulting in between-colony spatial segregation. However, little is known about within-colony variation in foraging behaviour that may arise from breeding locations. Using little penguins Eudyptula minor from a large colony (ca. 32 000 individuals) on Phillip Island (Australia), we present a novel approach combining GPS, diving, acceleration and bathymetry data. We investigated within-colony variation in 3-dimensional distribution of prey encounters and its consequences for foraging behaviour and breeding success. Over 1 breeding season, we simultaneously tracked 63 little penguins from 2 breeding sites located ~2 km apart and monitored their breeding success. We recorded 58 452 dives, of which 11 992 had prey en - counter events associated. Results revealed strong spatial foraging segregation between sites throughout the breeding season and differences between sites in prey encounter depth during chick-rearing (mean ± SE, 11.8 ± 0.2 m vs. 17.3 ± 0.3 m). Birds from one site foraged in deeper waters and apparently experienced higher levels of competition, resulting in lower prey en - counter rates and lower foraging efficiency (i.e. body mass gain after foraging trips), hence these birds seemed less successful. However, breeding success was high (>1.5 chicks fledged per pair) at both sites, indicating that food was not a limiting factor that year. Nonetheless, breeding success records over the last 12 yr showed that the site where birds foraged at deeper depths produced fewer chicks. Our findings highlight the importance of understanding small-scale spatial segregation to capture foraging behaviour variation within large seabird colonies.

The risk of rodent introductions from shipwrecks to seabirds on Aleutian and Bering Sea islands

Accidental introductions of rodents present one of the greatest threats to indigenous island biota, especially seabirds. On uninhabited remote islands, such introductions are likely to come from shipwrecks. Here we use a comprehensive database of shipwrecks in Western Alaska to model the frequency of shipwrecks per Aleutian and Bering Sea island, taken as a proxy for the threat of rodent introductions, using physical variables, and the intensity of nearby fishing traffic and activity as predictors. Using data spanning from 1950 to 2013, we found that shipwrecks were particularly common in the 1980s to early 2000s, with a major peak in wrecks during the late 1980s. Amount of fishing activity within 5 km of an island was the strongest predictor of shipwrecks, followed by the strength of tidal currents and density of large-vessel traffic. Islands with the highest frequency of shipwrecks are all in the eastern Aleutians, including Unimak, Unalaska, and Akun Islands. By contrast, the largest seabird colonies are in the western Aleutian and Pribilof Islands, including Buldir, Kiska, and Saint George islands. Multiplying the frequency of a shipwreck by the number of seabirds breeding per island provides a measure of risk. The risk of rodent introductions from shipwrecks to seabirds was then greatest for Saint George (Bering Sea), Buldir (Western Aleutians) and Saint Matthew islands (Bering Sea). Keeping these high-risk islands rodent free would maintain their high a conservation value. Most islands with a high predicted frequency of shipwrecks already have established rodent populations and therefore few remaining seabirds. Of those islands with established rodent populations, Attu and Kiska Islands would make suitable targets for eradication, given their relatively low expected frequency of shipwrecks for their size. Further improvements in rat prevention on vessels and shipping safety would benefit the economy, human health and safety, and to the long-term conservation of island ecosystems.

Daily and Annual Habitat Use and Habitat-To-Habitat Movement By Glaucous-Winged Gulls At Protection Island, Washington

Central questions of ecology concern how and why organisms distribute themselves in time and space. Answers to these questions contribute to our understanding of the fitness of organisms and provide baseline information against which to compare future distributions in the face of environmental change. Here we characterize daily and yearly fluctuations in counts of Glaucous-winged Gulls (Larus glaucescens) in 5 connected habitats associated with a large seabird colony in the Salish Sea, Washington State. Daily fluctuations in the 5 habitats differed markedly and were driven by day of year, time of day, solar elevation, tide height, barometric pressure, and ambient temperature. Seasonal peak numbers in all habitats occurred between mid-March and mid-September. No gulls remained on their breeding territories past late September, and few gulls remained on the island between late September and mid-January. Numbers rose steadily from early February to March.

Environmental DNA as a valuable and unique source of information about ecological networks in Arctic terrestrial ecosystems

Arctic terrestrial ecosystems are particularly vulnerable to the effects of ongoing and predicted climate changes. The current states of environmental biodiversity and ecological networks in the Arctic need to be known and understood to monitor how they change and how these changes may influence the particular components of the ecosystem. Despite the fact that the Arctic tundra is generally poor in nutrients, it has a surprisingly high biodiversity, especially of invertebrates and microorganisms. Besides macroclimatic features, there may be local factors influencing biodiversity, such as microclimate, water availability, or large seabird colonies depositing guano. This last can have a substantial impact on the soil’s physicochemical features, and consequently the distribution, number, and diversity of tundra-associated plants and animals in the vicinity of the colony. Changes in the Arctic biodiversity and the functioning of the ecosystem at all trophic levels are difficult to investigate using traditional methods. In this review, we discuss how modern molecular techniques, including next generation sequencing, influence our ability to investigate and understand this ecosystem at both the micro- and the macroscale and how they can complement the more traditional approaches to studying ecological networks in the Arctic.

Seabirds supply nitrogen to reef-building corals on remote Pacific islets

Seabirds concentrate nutrients from large marine areas on their nesting islands playing an important ecological role in nutrient transfer between marine and terrestrial ecosystems. Here we investigate the role of guano on corals reefs across scales by analyzing the stable nitrogen isotopic (δ15N) values of the scleractinian coral Pocillopora damicornis on fringing reefs around two Pacific remote islets with large seabird colonies. Marine stations closest to the seabird colonies had higher nitrate + nitrite concentrations compared to more distant stations. Coral and zooxanthellae δ15N values were also higher at these sites, suggesting that guano-derived nitrogen is assimilated into corals and contributes to their nitrogen requirements. The spatial extent of guano influence was however restricted to a local scale. Our results demonstrate that seabird-derived nutrients not only spread across the terrestrial ecosystem, but also affect components of the adjacent marine ecosystem. Further studies are now needed to assess if this nutrient input has a positive or negative effect for corals. Such studies on remote islets also open fresh perspectives to understand how nutrients affect coral reefs isolated from other anthropogenic stressors.

Polar bears observed climbing steep slopes to graze on scurvy grass in Svalbard

ABSTRACTIt is well known that polar bears feed on vegetation. Here, I report novel observations of polar bears grazing on polar scurvy grass (Cochlearia groenlandica) at the foot of a large seabird colony on a cliff on Spitsbergen, Svalbard, in the summers of 2005, 2006, 2009, 2014 and 2015. Why they choose such energy-costly climbing to feed on plants is not clear. One possibility is that they may be suffering from vitamin C deficiency and are searching for this particular plant, which has a high level of this vitamin. Another, but not exclusive reason, is that vegetation containing scurvy grass is abundant enough to be efficiently grazed by such unspecialized plant-eaters as polar bears only on such relatively inaccessible, steep slopes below seabird colonies. Most of the lowland and gently sloping tundra areas in Svalbard are overgrazed by geese and reindeer, the populations of which have increased considerably as a consequence of climate amelioration. Large seabird colonies are known to attract animal...

Cliff-nesting seabirds influence production and sediment chemistry of lakes situated above their colony

Seabirds that congregate in large numbers during the breeding season concentrate marine-derived nutrients to their terrestrial nesting sites, and these nutrients disperse and enhance production in nearby terrestrial, freshwater and marine ecosystems. In the Canadian Arctic, large seabird colonies (>100,000 breeding pairs) nest on cliff faces that drain directly in the ocean, ultimately returning the nutrients back to the marine environment from which they were derived. However, strong winds blowing up cliff faces could transport nutrients up in elevation and onto surrounding terrestrial and aquatic environments. Here, we assess the degree to which seabird nutrients and metals have been delivered to coastal lakes near Hudson Strait (Nunavut, Canada) over the past century. Three lakes located at a higher elevation and increasing distance from a thick-billed murre (Uria lomvia) colony (~400,000 breeding pairs) were sampled for surface water chemistry. In addition, algal assemblages, nitrogen isotopes, and metal/metalloids were analyzed in four dated sediment cores. Elevated nutrients and major ions, as well as an enriched δ15N signature in the sediment cores, were measured in the lake <100m from the cliff, whilst no comparable changes were recorded in lakes >1km from the seabird colony. In contrast, similar oligotrophic and benthic diatom assemblages were identified in all three lakes, suggesting that diatoms were not influenced by enhanced nutrient inputs in this Arctic environment. Chemical tracers (e.g., total mercury) and algal assemblages in the lake near the colony suggest climate warming since ~1950 was the most likely driver of limnological changes, but this effect was muted in the more distant lakes. These pronounced changes in the seabird-impacted lake suggest that, with warming air temperatures and diminished lake ice cover, longer growing seasons may allow for aquatic organisms to more fully exploit the seabird nutrient subsidies.

Differential responses of seabirds to environmental variability over 2 years in the continental shelf and oceanic habitats of southeastern Bering Sea

Abstract. Seasonal sea-ice cover has been decreasing in the southeastern Bering Sea shelf, which might affect ecosystem dynamics and availability of food resources to marine top predators breeding in the region. In this study, we investigated the foraging responses of two seabird species, surface-foraging red-legged kittiwakes Rissa brevirostris (hereafter, RLKI) and pursuit-diving foraging thick-billed murres Uria lomvia (TBMU) to different marine environmental conditions over 2 years. At-sea distributions of RLKI and TBMU breeding on St. George Island, the largest seabird colony in the region, were recorded using GPS loggers, and blood samples were taken to examine their physiological condition and isotopic foraging niche in a given year. Between the study years, winter ice retreated earlier and summer water temperatures were relatively warmer in 2014 compared to those in 2013. RLKI foraging occurred mostly over the oceanic basin in both years. TBMU, however, foraged mostly over the shelf but showed a relatively higher use of the shelf break and oceanic basin in 2013. The foraging distances from the colony peaked at 250–300 km in 2013 and bimodally at 150–250 and 300–350 km in 2014 for RLKI and tended to be farther in 2013 compared to those in 2014 for TBMU. Plasma levels of corticosterone did not differ between the years in RLKI but differed in TBMU, showing higher levels of physiological stress incurred by murres in 2013, the year of relatively cooler sea surface temperatures with later sea-ice retreat. δ13N (a proxy of trophic level of prey) did not differ between the years in either RLKI or TBMU. These results suggest that the response of ecosystem dynamics to climate variability in the southeastern Bering Sea may differ between the ocean basin and continental shelf regions, which, in turn, may generate differential responses in seabirds relying on those habitats for foraging.

Evidence of seabird guano enrichment on a coral reef in Oahu, Hawaii

Seabirds and coral reefs are two of the most threatened marine communities on earth, and they co-occur on many tropical islands and subtropical islands and atolls. Seabirds concentrate marine-derived nutrients on breeding islands in the form of feces (guano), and these nutrients dramatically alter terrestrial ecosystem ecology. Recent work in the remote Pacific indicates seabird-derived nutrients may also subsidize nearshore coral reefs, but the consequences of guano on complex, anthropogenically modified coral reefs are unknown. The impact of seabird guano on nearshore coral reefs around Moku Nui, an islet with a large seabird colony in Oahu, Hawaii, was investigated in comparison with coral reefs around three islets with lower seabird abundance. Reefs in close proximity to Moku Nui (where thousands of wedge-tailed shearwaters, Puffinus pacificus, breed) had greater concentrations of dissolved phosphate in seawater and greater δ15N in adjacent subtidal macroalgae relative to reefs next to smaller breeding colonies. However, dissolved nitrate was not different among islets. These results indicate that seabirds may be a source of nutrients for the waters surrounding Moku Nui that are already inundated with local and global stressors.