Associating Sound with Food in the Antillean Grackle, Quiscalus niger brachypterus Cassin, 1867 (Aves: Passeriformes: Icteridae)

The Greater Antillean Grackle, Quiscalus niger brachypterus, is one of the most common birds in urban habitats in Puerto Rico. This species is considered omnivorous and has an ample diet. The bird is quite opportunistic on its feeding habits and foraging patterns. From 2012-2014, while conducting work in a sorghum and corn field in the municipality of Santa Isabel, we observed the Antillean Grackle appear in multiple times just minutes after a plowing tractor had begun its work. It seems that the bird has learned to associate the noise produced by the vehicle with food exposure, as while plowing the machine will stir up a large variety of invertebrates and vertebrates from the soil. After Hurricane Maria, at the municipalities of Caguas, Juncos, and Humacao, we noticed that grackles have apparently learned to associate the noise produced by gas lawn mowers and trimmers with food, as those machines expose, injure, and kill many small animals which are part of the grackle’s diet in urban areas. At Caguas and Juncos, grackles waited until the gardeners finished their work to begin feeding on lawns, while at Humacao, grackles have been observed following gardeners using the machines, probably because of the absence of other potential urban predators. The Antillean Grackle seems to be an opportunist innovator with great ability to solve problems. A total of 19 innovations are reported on the genus Quiscalus, making it the second most innovative passerine genus after Corvus, in North America. Resumen: El Mozambique, Quiscalus niger brachypterus, es uno de los pájaros más comunes en hábitats urbanos en Puerto Rico. La especie es considerada omnívora y tiene una dieta amplia. El ave es sumamente oportunista en sus hábitos alimentarios y patrones de forrajeo. De 2012-2014, mientras trabajábamos en un sembradío de sorgo y maíz, en el municipio de Santa Isabel, observamos en muchas ocasiones a mozambiques aparecer minutos después, que un tractor comenzaba a arar. Todo parece indicar que las aves aprendieron a asociar el ruido que produce la máquina, con la exposición de alimentos, mientras el arado levanta del suelo una amplia variedad de vertebrados e invertebrados. Luego del huracán María, en los municipios de Caguas, Juncos y Humacao, notamos que los mozambiques habían aprendido a asociar el ruido producido por podadoras y recortadores manuales de grama con la exposición, de organismos de los cuales se alimenta el ave en áreas urbanas. En Caguas y Juncos, las aves esperaron que los jardineros terminaran su trabajo, antes de invadir el césped, mientras que en Humacao, los mozambiques seguían a los jardineros, probablemente debido a la ausencia de otros 1 Submitted on June 13, 2020. Accepted on June 25, 2020. Last revisions received on August 1, 2020. 2 Department of Biology, University of Puerto Rico, Humacao, Puerto Rico 00792. E-mail: raperezrivera@yahoo.com . 3 Department of Education of Puerto Rico, P. O. Box 190759, San Juan, Puerto Rico 00919-0759. Email: amolina197896@gmail.com . DOI: 10.9784/LEB8(2)PerezRivera.01 Electronically available on August 31, 2020. Mailed on August 31, 2020. Life: The Excitement of Biology 8(2) . 71 depredadores potenciales. El mozambique es un ave oportunista, innovador con gran habilidad para resolver problemas. Un total de 19 innovaciones han sido reportadas en el género Quiscalus en Norte América, siendo luego del género Corvus, el segundo paseriforme más innovador en patrones de conducta. Introduction The Greater Antillean Grackle, Quiscalus niger (Boddaert, 1783), occurs from the Cayman Islands (except Cayman Brac), throughout the Greater Antilles, including the island of Vieques, in Puerto Rico (Raffaele et al. 1998, Keith et al. 2003). Six subspecies of Q. niger are recognized, including Q. n. brachypterus Cassin, 1867 from Puerto Rico (Gill and Donsker 2019). In Puerto Rico, this bird is known by many names including mozambique (the official name) and the most common, chango. This blackbird with yellow eyes has an ample distribution in Puerto Rico and can be seen in almost every habitat except in dense internal forests (Oberle 2010). It is one of the most conspicuous species in urban habitat and usually it is observed in groups (Rivera-Cianchini and Mojica Sandoz 1981, Oberle 2010). The species is considered omnivorous and has an ample diet (Wetmore 1916, Pérez-Rivera 2000). Lack (1976) already noticed that, in Jamaica, these birds were quite opportunistic on their feeding habits and foraging patterns. Ducatez et al. (2015) have found that grackles are highly intelligent and easily learn how to get access to food. Overington et al. (2009) makes the genus Quiscalus the second most innovative passerine genus after Corvus in North America. While Lefebvre et al. (2016) considered the Icteridae second in its capability to innovate in a ranking of bird families within the clade of oscines, or songbirds, with easily visible nine primary feathers. This work reports casual observations in our neighborhoods, at Bairoa Park, Caguas (from this point forward referred to as Bairoa), Jardines de Ceiba Norte, Juncos (from herein on, Juncos), the campus of the University of Puerto Rico in Humacao (herein abbreviated, UPRH), and 3rd Millennium Genetics (referred to as 3MG), which is located at the Alomar Farm, Road 1 km. 101.7, Santa Isabel. The first three localities have been described in literature (Pérez-Rivera 2000, 2018, 2019). Santa Isabel is a coastal municipality, about 27 km from Ponce. The Alomar Farm is part of the coastal plain, rich in organic soil which is planted with experimental seeds, particularly of sorghum and corn. In the years 2012-2014, while conducting an assessment of the possible impact of wind turbines on birds in a sorghum and corn field at 3MG, many times we observed Cattle egrets, Bubulcus ibis (Linnaeus, 1758), and Antillean Grackles to appear just minutes after a plowing tractor have begun its work. The birds followed the tractor and consumed the earthworms, insect (beetle larvae), spiders (small tarantulas), centipedes, and even pieces of reptiles, and other unidentified animals that were stirred up, injured, or otherwise compromised by