Bobolink (Dolichonyx oryzivorus) Declines Follow Bison (Bison bison) Reintroduction on Private Conservation Grasslands

Among the most rapidly declining birds in continental North America, grassland birds evolved with American bison (Bison bison) until bison nearly became extinct due to overhunting. Bison populations have subsequently rebounded due to reintroductions on conservation lands, but the impacts of bison on grassland nesting birds remain largely unknown. We investigated how bison reintroduction, together with other land management and climate factors, affected breeding populations of a grassland bird species of conservation concern, the Bobolink (Dolichonyx oryzivorus). We quantified population changes in Bobolinks over an 18-year period in conservation grasslands where bison were reintroduced, compared with adjacent grasslands grazed by cattle and where hay was harvested after the bird breeding season. Four years after bison reintroduction, the bison population in the study area had doubled, while Bobolink abundance declined 62% and productivity declined 84%. Our findings suggest that bison reintroduction as a conservation strategy may be counterproductive in grassland fragments where overgrazing, trampling, and other negative impacts drive declines in grassland breeding birds. Where bird conservation is an objective, small grassland reserves may therefore be inappropriate sites for bison reintroduction. To maximize conservation benefits to birds, land managers should prioritize protecting grassland birds from disturbance during the bird breeding season.

FIFTH REPORT OF THE COMMITTEE FOR ECUADORIAN RECORDS IN ORNITHOLOGY (CERO), WITH COMMENTS ON SOME PUBLISHED, UNDOCUMENTED RECORDS

Wepresent new distributional records of birds in Ecuador evaluated by the Committee for Ecuadorian Records in Ornithology (CERO) from November 2017 through June 2019. This report includes two species new to Ecuador (Pelecanoides garnotii, Conirostrum margaritae), five species with first documented country records (Thaumastura cora, Anous minutus, Setophaga pensylvanica, S. virens, Spiza americana), two species with first documented Galapagos records (Oceanodroma hornbyi, Egretta tricolor), remarkable range extensions for 15 species (Amazilia amazilia, Aramus guarauna, Vanellus chilensis, Attagis gayi, Anous stolidus, Sterna hirundo, Thalasseus elegans, T. sandvicensis, Eurypyga helias, Mycteria americana, Plegadis falcinellus, Gampsonyx swainsonii, Rosthramus sociabilis, Glaucidium peruanum, Thlypopsis sordida), new records of 16 rare species (Oressochen jubatus, Spatula cyanoptera, Podiceps major, Stercorarius longicaudus, Larus belcheri, Pelagodroma marina, Oceanodroma markhami, Egretta rufescens, Plegadis ridgwayi, Buteo swainsonii, Megascops koepckeae, Tyrannus albogularis, Setophaga castanea, Dolichonyx oryzivorus, Icterus chrysater, I. galbula) and additional records for 8 species. Finally, we invalidate previous records of Pyrilia pyrilia published in different sources, reject records of six species submitted to CERO, and discuss six previously published, undocumented records that might prove erroneous. CERO revises and updates the country bird list, which currently stands at 1696 species (1642 confirmed and documented; 54 undocumented).

A 137-Year History of the Summer Avian Community at the Winous Point Marsh, Port Clinton, Ohio, USA

The Winous Point Marsh Conservancy and the Winous Point Shooting Club, with landholdings in both Sandusky and Ottawa Counties, Ohio, has completed a survey of the summer resident bird population on the property 4 times spanning 137 years. Although achieving a true census is unrealistic, these surveys have provided a unique, long-term history of changes in the avian community in northwest Ohio since the 1880s. Surveys were completed in 1880, 1930, 1960, and 2017. Draining and deforestation of the wetlands in northwest Ohio, by the late 1870s, resulted in the loss of many forested-wetland dependent species such as Blue-gray Gnatcatcher (Polioptila caerulea), Solitary Sandpiper (Tringa solitaria), and Northern Waterthrush (Parkesia noveboracensis) after the 1880 survey. Intensification of agricultural practices after the 1930 survey likely resulted in the loss of the early successional habitat that was associated with smaller, less intensive, agricultural practices and consequently the loss of many grassland nesting species such as Bobolink (Dolichonyx oryzivorus), Eastern Meadowlark (Sturnella magna), Northern Bobwhite (Colinus virginianus), Blue-winged Teal (Anas discors), Northern Pintail (Anas acuta), and Northern Shoveler (Anas clypeata). Several new species were documented during the 2017 survey including Osprey (Pandion haliaetus), Sandhill Crane (Antigone canadensis), Trumpeter Swan (Cygnus buccinator), and American White Pelican (Pelecanus erythrorhynchos). This long-term dataset provides a unique opportunity to investigate the avian immigration, extirpation, and recolonization of a specific site over the past 137 years, providing insight into how landscape-level habitat changes affected the avian community.

Diet of the Bobolink (Dolichonyx oryzivorus) in rice fields on its wintering grounds in Argentina

Winter diet of Bobolinks (Dolichonyx oryzivorus), a bird considered a pest of rice fields, is known to consist primarily of seeds. However, it is not yet possible to establish the extent to which non-rice plants and animal components contribute to its diet. To contribute to these issues, we studied the diet of the Bobolink found in rice fields on its wintering grounds in Santa Fe, Argentina, to provide information on (i) the composition of the diet and (ii) the relative importance of plant and animal components in the diet and of the different prey categories. We captured Bobolinks with mist nets and obtained samples of stomach contents by warm water and emetic-based regurgitation to determine the composition of the diet (n = 46 samples) and the importance of the different prey (n = 25 samples), mainly during March, just prior to northbound migration. We confirmed that the Bobolink’s diet in this region during this period is predominantly herbivorous (97%) and rice-based (55%), although it also consumes a large number of seeds of non-cultivated plants that represented 42% of the diet. Invertebrates, although of less importance than plant components (3%), had been consumed by 97% of captured individuais. Our results document the importance of non-cultivated plants and animal prey in the diet of Bobolinks in addition to rice.

Trends in Bird Densities at a Remnant Fescue Grassland in Saskatchewan

Populations of grassland birds in North America have declined greatly in the past five decades. Hypothesized drivers of decline include habitat loss, fragmentation, and adverse impacts from human activities. At a remnant fescue grassland in Saskatoon, Saskatchewan numbers of Savannah Sparrow (Passerculus sandwichensis), Western Meadowlark (Sturnella neglecta), Brewer’s Blackbird (Euphagus cyanocephalus), and Vesper Sparrow (Pooecetes gramineus) have been stable. Numbers of clay-colored Sparrow (Spizella pallida) have increased since the 1960s. Sprague’s Pipit (Anthus spragueii), Upland Sandpiper (Bartramia longicauda), and Burrowing Owl (Athene cunicularia) are no longer present. Baird’s Sparrow (Ammodramus bairdii), Bobolink (Dolichonyx oryzivorus), and Horned Lark (Eremophila alpestris) have become irregular visitors. In the past 50 years, 91 species have been observed displaying territorial behaviour, feeding, nesting, or migrating at this remnant native grassland. With encroaching urban development and increased human influence at the prairie and surrounding area, the impacts on the bird communities at the site in the future are unknown.