Evidence of breeding activity of subadult Turdus thrushes in Argentina

Little is known about the age at which many Neotropical bird species first attempt to breed. We evaluated the breeding condition of 515 adult and subadult males and females among four species of Turdus thrushes (T. nigriceps, T. chiguanco, T. amaurochalinus and T. rufiventris) in Tucumán, Argentina during three breeding seasons (2015 to 2018). We registered a total of 126 individuals with brood patches and cloacal protuberances, which accounted for 24.5% of thrushes in breeding condition that we sampled. Forty thrushes had a brood patch (31.7% of those in breeding condition), of which 11 were subadults (8.7%). Eighty-six thrushes (68.3%) had a swollen cloacal protuberance, 18 of which were subadults (14.3%). Only a few of the subadults in breeding condition built nests, incubated eggs or raised nestlings. Of 130 nests we found, only 3 belonged to a subadult thrush (in all cases, a subadult female with an adult social mate), one of which was successful. Further research on these patterns among various Neotropical bird species could lead to important insights into the life history strategies that characterize different populations, and how these ultimately affect their population dynamics.

Fitness heterogeneity in adult Snow and Ross’s geese: Survival is higher in females with brood patches

Life-history theory broadly predicts a fitness tradeoff between costs of raising offspring and parental survival. Waterfowl with precocial young face particularly high costs of egg production, incubation, and brood-rearing, but not all evidence supports a corresponding decline in survival. We used multi-state mark–recapture–recovery models to estimate annual probabilities of survival, reported mortality, and transition between 2 states for female Ross’s Geese (Anser rossii) and Lesser Snow Geese (A. caerulescens caerulescens) that attempted nesting near Karrak Lake, Nunavut, Canada. States were possession of a brood patch (high likelihood of successful nesting, “B”) vs. no brood patch (attempted nesting but failed, “N”). Based on over 43,000 birds marked from 2000 to 2015, we found that females of each species with a brood patch had consistently higher probabilities of survival than those without, subsequent to capture in early August. Virtually all of the state differences in survival were due to nonhunting mortality. These patterns are consistent with the concept of variable individual quality impacting vital rates across multiple seasons. Higher survival of females with brood patches may be linked to greater breeding success but also to a hypothesized dominance advantage afforded to family groups of geese during winter. Moreover, although hunting pressure can play a key role in regulating Arctic goose populations, it does not appear to affect this relationship between inferred breeding state and survival. Instead, coincident with recent declines in harvest rate in these populations, higher individual quality of breeding females appears to outweigh the higher hunting vulnerability of presumed parents with young. The potential influence of social dominance in reducing natural winter mortality among families may thus contribute to the survival advantage seen in successful, relative to failed, breeders.

Seasonality, biology and threats to Sicalis luteola (Sparrman, 1789) (Aves, Thraupidae) in northeastern Brazil

Sicalis luteola occurs from Mexico to South America. In the Northeastern Brazilian region its biology, population dynamics and threats are poorly known. The subspecies S. luteola luteiventris apparently migrates northward during austral winter. The specific aims of this work were: 1) to verify the seasonality of the species; 2) to analyze information on molting and breeding, and 3) to check the main threats to this bird in northeastern Brazil. The highest number of records were in March, April, and May (51.12%) and the lowest in November and December (3%).We found a greater population peak in April in the states of Rio Grande do Norte and Ceará, and in April and May in Pernambuco. In Paraíba there was not an apparent seasonal variation in frequency. We captured 66 individuals, all adults, being 38 males and 28 females. 30% of the captured birds showed contour feathers molt, mainly on the head. A total of 23 individuals had brood patch, all being females. Six nests were found and four contained two to three eggs. We found that the main threat is the illegal trade. Our findings may support conservation plans for this bird in the region.