Ornitología Neotropical

BREEDING BIOLOGY OF THE LOGGERHEAD SHRIKE LANIUS LUDOVICIANUS IN CENTRAL MEXICO

Sun, 17 Mar 2024 00:00:00 -0700

The Loggerhead Shrike Lanius ludovicianus has an exceptionally broad distribution in North America, with the southernmost populations found in central Mexico. The species has experienced severe declines throughout its range, and thus, is of conservation concern, particularly in USA and Canada. Life history data is scarce for Mexico, where both resident and migratory populations are found. In this study we provide information on the breeding biology of a population of Loggerhead Shrikes near the southern limit of its distribution in central Mexico. Based on data from 70 nests over three breeding seasons (2007–2009), we estimated the average nest density as 0.85 nests/ha with most nests built in mesquite trees Prosopis laevigata. Average clutch initiation date was March 28, with variation among years. The breeding period averaged 3.5 months, starting at the end of February, and extending to early June. The laying period averaged 4.6 days, incubation averaged 18 days, and the average brooding period 16.6 days, for a total average of 39.2 days from egg laying to the end of brooding. Clutch size averaged 4.1 eggs (range 2–5) with a mode of four eggs. The nesting success for the three years combined was 64.3% (range 54.5–68.9%). Daily survival rate was estimated to be 0.749 using logistic exposure. The average number of fledglings at successful nests was 1.5. Predation was the main cause of nest failure, accounting for 35.7% of all active nests. In general, life history traits of this Mexican Loggerhead Shrike population are like those reported for breeding populations in more northern parts of its range; however, clutch size was smaller and average incubation period was significantly longer, probably because of latitudinally-related environmental factors.

BIOLOGÍA REPRODUCTIVA DEL CHINCHERO ENANO O CHINCHERO EXCAVADOR XIPHORHYNCHUS FUSCUS

Sun, 17 Mar 2024 00:00:00 -0700

Despite recent advances, the knowledge scarcity on Furnariidae forest species reproduction continues to bias ideas and limit the understanding of avian life history. We studied the reproductive biology of the Lesser Woodcreeper (Xiphorhynchus fuscus; Dendrocolaptinae), which nests in tree cavities, to contribute observations toward ideas about evolution and ecology. In the Atlantic Forest of Argentina (2007–2022), we inspected 26 nests (total: 333 visits), color-banded nine adults, conducted 180 h of focal observations at 11 nests, and analyzed patterns of nest survival and parental care using linear models in R. Lesser Woodcreepers laid two or three white eggs (mean±SE = 2.8±0.1; N = 16) on a bed of bark flakes. One adult (possibly female) carried out construction, incubation, feeding, and nest hygiene, but we frequently observed a second adult (possibly male) singing from 'preferred' perches, sometimes approaching the nest tree in response to alarm calls from the nest. Attending adults brought bark to their nests throughout incubation (19 days) and occasionally during nestling (21 days; range: 20–23). In the absence of adults, eggs and young nestlings were left covered with bark. Nest attention (daytime percentage an adult was inside the cavity) was 63±3% during incubation, fell to 38±9% in the first 4 days after hatching, and approximately 0% after nestlings were 10 days old and had open pin feathers. Nestlings were fed almost exclusively arthropods, and the feeding rate increased as brooding declined. Nest survival was 0.984 (95% CI: 0.970–0.992) daily or 0.50 (0.26–0.70) for the nesting period. For four of six broods, when nestlings fledged, a second adult (possibly a male) participated minimally. Our observations cover the mating system and division of parental care in Furnariidae, the advantages of covering eggs and nestlings, and the possibility that males increase parental care during the vulnerable fledgling stage.

NECTAR ROBBING BY THE RED-TAILED COMET SAPPHO SPARGANURUS: THE VALUE OF CITIZEN SCIENCE TO DOCUMENT INFREQUENT BEHAVIOR IN BIRDS

Luciana Telleria, Rodrigo Calbimonte, Flavia Montano-Centellas — Sun, 17 Mar 2024 00:00:00 -0700

Nectar robbing by hummingbirds, the extraction of nectar using perforations instead of the corolla, is seldom documented in the literature. Here, we present the first photographic record of nectar robbing by the Red-tailed Comet Sappho sparganurus in Bolivia and examine published and photographic evidence of this behavior. We found no published evidence of nectar robbing by Red-tailed Comets in peer-reviewed literature. However, we found that about 4% of the photographs of hummingbird-flower interactions involving this species on citizen science platforms showed clear nectar robbing behavior. Our results suggest that nectar robbing is not an uncommon behavior for the Red-tailed Comet and highlight the hidden, yet immense, value of citizen science photographic databases to document avian natural history and behavior.