Editor Likes
Editor-in-Chief K. S. Gopi Sundar showcases papers that he particularly liked . Check out his picks from each Waterbirds journal issue below.
There were 7,837 pairs of Laughing Gulls found breeding on a dredge-spoil island at Bahia Tobari. Photo credit: German Leyva-García
Waterbirds have a love-hate relationship with artificial intrusions such as canals. Additionally, regular dredging of such waterways is often regarded to be a destructive and disturbing activity. In this study, authors throw up fascinating findings of how waterbirds discovered, used and became attached to, as it were, with islands formed from dredge-sediments.
Eduardo Palacios, the corresponding author of the paper, remarked that “The dredge-spoil islands were colonized very rapidly by nesting birds and the occurrence and number of nesting bird species has been very dynamic. A large proportion of local fishermen did not agree on the creation of the islets, they now know more about the biological importance of these sites and value them.”
This paper shows how a simple choice – retaining dredge-sediment as islands – can often lead to human-related structures and activities becoming important and useful for waterbirds. No matter how destructive a particular human activity appears to us, some patient waiting and observing can help understand if waterbirds feel the same way.
Royal Terns, Elegant Terns, and Laughing Gulls on a dredge-spoil island at Bahia Tobari. Photo credit: German Leyva-García
The following papers are from Waterbirds VOL. 45 · NO. 4 | DECEMBER 2022
Wetlands were created from a burrow pit used for the building of the dam. Photo credit : SNC-Lavalin.
Dams to generate hydroelectricity are common the world over and may increase in response to technologies such as battery-operated vehicles that will require electricity. However, the impacts of these dams on waterbird populations are poorly understood. In this excellent study, authors use a classic before-after design that threw up surprising and hopeful results – waterbird breeding, especially density of broods, increased greatly after impoundment.
Corresponding author Lapointe pointed out: “Our study showed that, contrary to our predictions, the density of breeding pairs was reduced in the first year but after 10 years remained stable or slightly increased. However, the density of broods increased six-fold after impoundment. The lower water level fluctuations of the reservoir were similar to those of natural ponds, shallow waters were also created, and large water bodies likely offer better protection from mammalian predators for waterbird broods.”
This work shows the need to carefully document potential impacts of artificial impoundments that alter hydrologies, especially paying attention to mitigation measures. Such studies can help highlight the most efficient and useful mitigation – like creating wetlands as detailed in Sénéchal et al. (2022) – rather than only deploy common strategies like nestbox installations, which are important but likely have lesser impacts.
Nest boxes were installed along the reservoir in order to mitigate the impact of the creation of the reservoir on waterfowl. Photo credit : SNC-Lavalin.
Gull-billed Tern returning to the breeding colony with a western fence lizard, 2013. Photo by Matt Sadowski.
Perturbations in climate such as stronger El Niño events have caused collapse of fish populations which in turn are linked to higher seabird mortality in some locations. Such extreme events are predicted to become more regular. This begs the question of how seabirds such as the Gull-billed Terns Geochelidon nilotica will cope with sudden and severe changes in prey availability. Goodenough et al. (2022) carefully evaluated tern diet over seven years using regurgitated pellets and found that they shifted to a new diet during unusually warm years thereby allowing unimpeded reproduction during such anomalous years.
Goodenough, who co-authored this work, commented that “the diet paper was a labor of love. I think the most surprising result of the research was the ability of the Gull-billed Tern population to respond to such a drastic change in prey diversity and mitigate potential reproductive impacts by diet switching. The results reinforced with us authors just how important a role dietary plasticity can play in mitigating seasonal variation in resources.”
It is heartening that at least some species have the capability to be flexible with diet in the face of rapidly changing climate that is becoming the new normal. Studies such as this one shows the importance of relatively simple work carried out carefully over multiple years and that taking advantage of unusual weather events can help uncover a species’ behavioural boundaries.
Gull-billed Tern chick at nest with diet items spread around the nest. Photo by Kate Goodenough.
The following papers are from Waterbirds VOL. 45 · NO. 3 | SEPTEMBER 2022
Marsh birds in a Great Lakes coastal wetland with Phragmites invading. Photo credits: Dustin E. Brewer
Introduced plant species, such as Phragmites, can expand rapidly in wetland ecosystems providing considerable change of habitat conditions for waterbirds. Their spread and impacts, however, are moderated by water levels that can vary due to diverse factors such as human activity and climate.
In this study, Dinehart et al. (2022) monitored Phragmites cover alongside numbers of four waterbirds – Least Bittern (Ixobrychus exilis), Marsh Wren (Cistothorus palustris), Sora (Porzana carolina), and Virginia Rail (Rallus limicola) – in Lake Huron between 2002 and 2015. This time period included years before Phragmites invasion, years when the plant spread widely, and some years with very high water levels that caused the plant to die down offering an excellent natural experiment of how waterbirds respond to changing extents of Phragmites.
Communicating author Thomas Gehring says “We found that expansion of invasive Phragmites australis functioned as a broad-scale biotic factor that reduced marsh bird habitat nearly 40% across the landscape, and this expansion was only countered with rising Great Lakes water levels which increased marsh bird habitat up to 10%. Examining Phragmites expansion and retraction with natural fluctuations in Great Lakes water levels over a 14-year period was illuminating for better understanding these dynamic systems and informing restoration efforts.”
Juvenile Virginia Rail captured at a Great Lakes coastal wetland study site. Photo credits: Dustin E. Brewer
This study stands out for its long-term and landscape-scale approach, and its judicious application of ecologically scaled landscape indices to understand the responses of several important marsh waterbirds. The study is timely given that water levels in many wetlands are predicted to decline potentially improving conditions for rapid plant invasions.
Fulvous whistling ducks and Blue-winged Teals at the Lagoon of Zumpango. Both species are affected by the loud noises of firework festivities. Photo credit: Araceli J. Rodríguez-Casanova
Fireworks are globally ubiquitous and have become a central part of many kinds of festivities. There have been relatively few investigations into impacts of fireworks on waterbirds, but all the existing ones show one result – waterbirds and fireworks do not go together. In this study, authors conduct a before-after study of the potential impacts of fireworks on waterbirds at Zumpango lagoon in Mexico.
Authors noted a decrease in both species richness and waterbird abundance following the fireworks. Most of the decline occurred in locations closest to sites with fireworks, and most sites further away saw an increase in waterbirds following the events.
Clearly, some human-related disturbances are intolerable to waterbird communities. As authors correctly note, available studies should be adequate to dissuade the use of fireworks in areas with waterbirds, especially important sites such as the study area.
Preparation of firework-castle structures in the Lagoon of Zumpango. High-impact human festivities such as the “Burning of Judas” have negative consequences for thousands of birds, especially in the wetlands of central Mexico, which represent important refuges for resident and migratory birds. Photo credit: Araceli J. Rodríguez-Casanova
Black-vented Shearwater flying. Photo credits: Jorge Andres Morales Rico
Seabirds are famously pelagic outside their breeding season and are known to have vast home ranges. Thanks to their roaming habits, little was known of the ecology of most seabirds during migration. In this study, Rosas-Hernández et al. (2022) describe the moulting pattern of the Black-vented Shearwater (Puffinus ophisthomelas) and used isotopes in feathers to construct diets of male and female birds on their breeding and post-breeding periods.
Communicating author Cecilia Soldatini summarized the complex work very simply. “What I found very interesting is that sexes showed differences in their diet across the year. With females showing more plasticity than males having a larger isotopic niche during the more demanding reproductive period. Such a smart strategy to overcome resource shortages and warrant chicks and their own survival!”
The study has achieved significant improvements in the understanding of the very poorly studied Black-vented Shearwaters starting with a sound construction of basic moulting patterns going on to address a set of related ecological questions. Developing ecological studies that also robustly document unknown aspects of natural history is an important way to overcome the huge lacunae existing in seabird, indeed waterbird, understanding.
Black-vented Shearwater on water. Photo credits: Javier Eduardo Alcalá Santoyo
Siberian Crane No. “956”(Color ring No.) in 2015.10.8. Credit: Lianshan Li, taken in Xianghai, Jinling Province.
Waterbirds that undertake long distance migration require to make multiple decisions. These choices are broadly associated with two critical aspects: timing and route. These two aspects are getting trickier to navigate especially with changing land use occurring at continental scales and changing weather at global scales.
Li et al. tracked 10 Siberian Cranes Grus leucogeranus between 2014 and 2018 using GPS/GSM trackers providing the first detailed multi-year information on migration of the same individuals including start times, stop-over sites, and routes. The authors stated, “our results provide support for some seasonal plasticity in the timing of migration and flexibility in routes taken by migrating Siberian Cranes. Unexpectedly, the Siberian Crane migratory routes are flexible near the only wintering ground, but they are repeatable near the wide breeding grounds”. This work also identified two kinds of stop-over sites – those that were used regularly and for longer periods by most cranes, and those that were rarely used by few.
The study is a great example of simple natural history that provides compelling information to redesign conservation strategies based on the behaviour of this iconic migratory waterbird species. Authors have seized the opportunity by providing several clear suggestions that can improve protection of key sites while also supporting the well-being of the migrating Siberian Cranes.
Siberian Crane No. “951” in 2014.10.19. Credit: Lianshan Li, taken in Xianghai, Jinling Province.
The Eared Grebes and the Black-headed Gull on nests. Credit: Robert Gwiazda
Studying inter-species interactions in artificial habitats is not a popular subject, but as this paper shows, can be richly rewarding. Gwiazda et al. explored the factors that influence nesting success of the poorly studied Eared Grebes Podiceps nigricollis in carp ponds of Poland. Here, the grebes nested alongside terns and gulls making for a strange yet interesting ecological system.
Grebes preferentially nested in carp ponds with nesting gulls and terns, probably benefiting from the aggressive neighbours who could keep away potential predators. The overall breeding success of grebes, however, was low despite availability of adequate food. Gwiazda commented, “Breeding numbers of the Eared Grebe have decreased in Central Europe, and knowing the factors affecting nesting of this species on carp ponds is important for its protection. Carp in the 2nd and 3rd year of life may be food competitors for the Eared Grebe but surprisingly, the age of the reared fish had no effect on the number of nests and chicks of this species in the artificial waterbodies.”
Adult Eared Grebe and chick. Credit: Robert Gwiazda
The following papers are from Waterbirds VOL. 45 · NO. 1 | MARCH 2022
Loons fighting (photo: Daniel Poleschook, Jr. and Virginia R. Poleschook)
Sternal punctures (photo: Mark Pokras, DVM)
Loon fights over territories are the stuff of legend with jousts sometimes resulting in deadly injuries. It has long been suspected that only males engage in such aggressive interactions, but Higgins et al. provide a critical correction using post-mortem examinations of the sternum of dead birds involved in such fights.
Communicating author Mark Pokras remarked that “field studies had always focused on conspicuous aggression between territorial males. A major surprise of our necropsy studies has been the extent to which female loons are involved in serious, sometimes fatal aggressive interactions”.
The role of female birds in territoriality is increasingly being recognized as significant across a multitude of taxa. This study on loons adds evidence that severe aggression – the sort that ends in mortality – is gender-free. These findings complicate but help develop a fuller understanding of the contribution of each gender in the development of important behaviors such as mortal combat.
Waterbird aggregations in Cuba (photo: Dr. Martin Acosta Cruz)
Multi-species foraging bird aggregations, haphazard as they may look, usually have patterns with one or few species being the nuclear species. Forest birds have been studied carefully to understand the form and structure of such aggregations, with few such studies from wetlands and waterbirds.
Waterbird aggregations in Cuba (photo: Dr. Martin Acosta Cruz)
González et al. carefully document such aggregations in the largest natural wetlands in insular Caribbean and report the American White Pelican to be a nuclear species during the wet season. “This is the first time that the pelican is found to be a nuclear species. We also bring out the influence of season and hydrology in changing patterns of aggregations” report the authors.
Waterbirds observed over long durations and over multiple seasons as in this study can substantially improve our understanding of factors driving compositions of multi-species foraging flocks. Doing so in poorly explored regions such as Cuba is an added thumbs-up.