The Grey-bellied Comet (Taphrolesbia griseiventris) is a hummingbird species endemic to northern Peru and listed as Endangered by IUCN due to its small and fragmented population. Despite this, little has been attempted to increase knowledge of its natural history and ecology to provide current information and better evaluate its conservation status. Here, we used known curated records of the species from the literature to generate a model of its potential distribution using MaxEnt, and we then validated the model in the field through direct observation in selected areas. Where the species was confirmed, we conducted a habitat characterisation with field data, and a threat assessment of the landscape using secondary data in ArcGIS. We found five new records of the species in the department of La Libertad at two different sites, confirming a new population. The habitat mostly comprised Andean scrub (17.6%) throughout its distribution, and the main threat in the habitat was human-induced fires for agricultural purposes and as a means of waste disposal. Our findings revealed new information on the distribution of the species with a potential habitat occupancy of 4–6% within its range. Furthermore, areas that were previously reported to harbour a population of the species no longer showed records despite intensive searches in the field. Finally, we discuss the implications for its conservation. Our results indicated that conservation measures to protect the Grey-bellied Comet are urgently needed, especially the declaration of a reserve in La Libertad, which might be the only area where the species is reliably present with good quality habitat.

A central challenge to the study of animal aerodynamics has been the measurement of forces generated by flapping wings. Relative to wings of other birds, hummingbird wings are of particular interest in that the smaller species operate in more viscous regimes (5000<Re<10 000) for which substantial drag and reduced lift:drag coefficients might be expected. Lift and drag forces were measured on mounted hummingbird wings and wing models spinning in continuous tipwise revolution about the wing base. Lift coefficients tended to increase as wing models became more realistic (i.e. with sharpened leading edges and with substantial camber). Lift:drag ratios of real wings were substantially higher than those of wing models, suggesting morphological contributions of feathers to lift enhancement and drag reduction. At Re=5000, high values of the lift:drag ratio (8–16) at low angles of attack suggest that wings of hummingbirds are exceptionally good at producing lift.

The kidneys of Anna's hummingbird (Calypte anna) differ in several significant ways from those of other birds that have been examined. The kidneys of this nectarivore contain very little medullary tissue; 90% of the total volume of the kidneys is cortical tissue, with medulla accounting for only an additional 2%. More than 99% of the nephrons are the so-called ‘reptilian type’), which lack the loop of Henle. The few looped (‘mammalian type’) nephrons are incorporated into only a few medullary cones per kidney. The loopless nephrons are similar to those of other birds. However, the looped nephrons differ in that they lack the thin descending limb of the loop of Henle, which is found in other birds and is thought to play an important role in the countercurrent multiplier system in the avian kidney. Instead, the cells of the nephron segment following the pars recta of the proximal tubule resemble those of the thick ascending limb, with the large populations of mitochondria that are typical of transporting epithelia and no reduction in cell height. The absence of a descending thin limb in Anna's hummingbird is not necessarily a correlate of the hummingbird's liquid diet, because thin limbs have been documented in the kidneys of two other hummingbird species, the rufous hummingbird (Selasphorus rufus) and the broad-tailed hummingbird (Selasphorus platycercus). The functional correlates of the unique renal morphology in Anna's hummingbird warrant further study.