Microplastics in the diet of nestling double-crested cormorants (Phalacrocorax auritus), an obligate piscivore in a freshwater ecosystem

Anthropogenic debris, namely plastic, is a concern across aquatic ecosystems worldwide, with freshwater systems being understudied relative to marine systems. In this study, we quantified and characterized debris in the diet of double-crested cormorant chicks (Phalacrocorax auritus) from three sites in two of the Laurentian Great Lakes to (i) determine whether or not the diet of double-crested cormorants in the Laurentian Great Lakes includes anthropogenic debris, (ii) characterize the size, shape, and type of debris incorporated, and (iii) examine relationships between the amount of debris ingested and their proximity to industrial–urban centres. Overall, >86% of cormorants in our study had anthropogenic debris (mostly fibers) in their digestive tracts with no correlation between site and the amount of debris ingested. The ingested debris includes microplastics, natural fibres from textiles, and other anthropogenic materials (e.g., glass). To the best of our knowledge, this is one of the first studies to examine anthropogenic debris in a diving bird in the Laurentian Great Lakes and one of few studies investigating this in freshwater birds.

Survival, fidelity, and dispersal of Double-crested Cormorants on two Lake Michigan islands

Colony fidelity and dispersal can have important consequences on the population dynamics of colonial-nesting birds. We studied survival and inter-colony movements of Double-crested Cormorants (Phalacrocorax auritus; cormorants) nesting at Spider and Pilot islands, located 9 km apart in western Lake Michigan, during 2008–2014. We used live resighting and dead recovery data from both colonies, plus dead recoveries from throughout North America, in a multistate live and dead encounter model to estimate annual survival, inter-colony movements, plus temporary and permanent emigration to unmonitored sites. Annual survival averaged 0.37 (annual process variation, σ⌢=0.07) for hatch-year, 0.78 (σ⌢=0.08 ) for second-year, and 0.89 (σ⌢=0.04 ) for after-second year birds. The best approximating model recognized only 2 age classes for transition probabilities, indicating little difference in fidelity and movement probabilities after the natal year. Annual fidelity to Spider and Pilot islands averaged 0.53 (σ⌢=0.17 ) and 0.48 (σ⌢=0.24) for second-year and 0.55 (σ⌢=0.23 ) and 0.62 (σ⌢=0.16 ) for after-second year cormorants, respectively, indicating substantial emigration for both age classes. For birds that dispersed, emigration was approximately equally divided among neighboring colonies, temporary emigration sites from which surviving birds subsequently returned, or permanent emigration sites from which birds never returned (but were still encountered through dead recoveries). Our results indicate that Double-crested Cormorants in the Great Lakes have tremendous potential to disperse, which may help to explain their rapid recolonization following historically low populations in the early 1970s.

EL PEZ BAGRE INVASIVO PTERYGOPLICHTHYS PARDALIS (SILURIFORMES: LORICARIIDAE) COMO PARTE DE LA DIETA DEL CORMORAN PHALACROCORAX AURITUS (PHALACROCORACIDAE) EN DOS REGIONES TROPICALES DE MÉXICO

El bagre Pterygoplichthys pardalis (Castelnau 1855) es una especie de pez invasivo en varias regiones de México, incluidoslos sistemas de lagunas fluviales del estado de Campeche en el sureste y en Mazatlán, Sinaloa, en el noroeste de este país.Aunque varios estudios han mencionado los impactos negativos de este pez invasor en el medio acuático, existen pocosinformes sobre los depredadores naturales que pueden ayudar a controlar estas poblaciones de peces. En este estudio,investigamos la depredación por alimentación de peces P. pardalis por cormoranes de doble cresta Phalacrocorax auritus(Lesson, 1831) en el río Palizada, al sureste del Golfo de México y la laguna del Camarón en el noroeste de México.La evidencia de alimentación encontrada en el contenido estomacal de estas aves puede indicar que los hábitos dealimentación podría adaptarse a los cambios en la comunidad de peces residentes después de la introducción del bagreinvasivo a estos nuevos ambientes acuáticos y las aves están explotando una nueva fuente de alimento como componentede su dieta.