Riqueza de avifauna e atividade reprodutiva de Chroicocephalus cirrocephalus (Vieillot, 1818) - Aves, Laridae (gaivotas-de-cabeça-cinza) em salina artificial no litoral da Costa Branca do Rio Grande do Norte, Brasil

Abstract

In this work, a colony of gray-headed gull (Chroicocephalus cirrocephalus) established in an artificial saline area of Rio Grande do Norte was monitored from July/2019 to June/2020. During this period, the presence of all birds that frequented the sampling area and its surroundings was recorded, and individuals of the species C. cirrocephalus in reproductive activity were monitored. We made two chapters. In the first chapter, information about the beginning of the nesting and laying period, the dam used in the saline, number of eggs and nestlings, egg morphometry and variables that influence the amount of eggs deposited were noted. The main hypotheses tested were (i) the number of eggs is determined by the abundance of gulls and the month of the year that would indicate the peak of the species' reproductive activity; (ii) dikes closer to the sea and the estuary and, therefore, to the natural environment of the gulls and to the food source they are more used by the gulls for nesting and laying; and (iii) that the morphometric measurements of the eggs vary according to the reproductive stage and clutch size. The results indicated eight months of reproductive activity and that not only the number of gulls and the month sampled determine the amount of eggs, but also the average monthly temperature, the total monthly rainfall, the proportion of vegetation cover as well as the dike used. In particular, the dikes most used for laying are not those close to the sea and the estuary (refuting the second hypothesis), but those central to the saline, probably because they are less exposed and larger. The morphometry of the eggs indicated a difference only in the weight of the eggs between the 3 reproductive stages. This difference may indicate greater viability of laying, greater reproductive success of eggs and nestlings in the middle and final stages of laying, body size of females or the availability of food that would be smaller in the initial stage. The presence of 3 other species in reproductive activity was identified, one of them in mixed colonies with the grayheaded gulls and another 80 species were recorded foraging around the sampled area. These records resulted in chapter 2, which is a technical document in the form of a photographic guide of the avifauna recorded in the artificial saline.