Hummingbird migration and flowering synchrony in the temperate forests of northwestern Mexico

Background Many species of birds are morphologically and physiologically adapted for migration. Migratory movements of birds can range from thousands of kilometers, such as when birds migrate from wintering to breeding sites in summer, to several kilometers, such as when birds migrate among habitats in a single mountain system. The main factor that influences bird migration is the seasonal fluctuation of food resources; climate, predation, competition for resources and endogenous programming are also important factors. Hummingbirds are highly dependent on nectar, so their migration is likely correlated with the blooming of plant species. The ecological implications of altitudinal migration in the mountains of North America as well as the latitudinal migration of Selasphorus rufus through Mexico are still poorly understood. To explore these issues, over three non-consecutive years, we evaluated interannual variation in the phenologies of a latitudinal migrant (S. rufus) and an altitudinal migrant (Amazilia beryllina) and their visited plants. Methods We assessed the relationship between two migratory hummingbirds and flower abundance in 20 fixed-radius plots (25 m radius). All available flowers were counted along transects (40 × 5 m) inside each fixed-radius plot. Sampling was performed every 10 days from November 12 through February 20 of 2010–2011, 2013–2014 and 2015–2016, resulting in a total of 11 samples of each plot per period. Phenological variation and the relationships among hummingbird abundance, flower abundance and vegetation type were evaluated using a generalized additive mixed model. Results S. rufus abundance was related to sampling time in the first and third periods; this relationship was not significant in the second period. A. beryllina abundance was related with the sampling time over all three periods. The abundance of S. rufus hummingbirds was significantly related to the number of Salvia iodantha flowers. The abundance of A. beryllina hummingbirds was related to the number of S. iodantha and Cestrum thyrsoideum flowers and the total number of flowers. We found a non-significant correlation between S. rufus and A. beryllina abundance and vegetation types. Conclusion Contrary to expectations, the long-distance migration of S. rufus was not consistent over the sampling periods. The migration of S. rufus through the study region may be altered by changes in climate, as has occurred with other species of migratory birds. In the present study, the migration of S. rufus was correlated with the blooming of S. iodantha. In comparison, the altitudinal migrant A. beryllina responded to the availability of floral resources but was not associated with a particular plant. The migration of this latter species in the area probably depends on multiple factors, including climatic and demographic factors, but is particularly dependent on the supply of floral resources and competition for these resources

Implications of dominance hierarchy on hummingbird-plant interactions in a temperate forest in Northwestern Mexico

The structuring of plant-hummingbird networks can be explained by multiple factors, including species abundance (i.e., the neutrality hypothesis), matching of bill and flower morphology, phenological overlap, phylogenetic constraints, and feeding behavior. The importance of complementary morphology and phenological overlap on the hummingbird-plant network has been extensively studied, while the importance of hummingbird behavior has received less attention. In this work, we evaluated the relative importance of species abundance, morphological matching, and floral energy content in predicting the frequency of hummingbird-plant interactions. Then, we determined whether the hummingbird species’ dominance hierarchy is associated with modules within the network. Moreover, we evaluated whether hummingbird specialization (d’) is related to bill morphology (bill length and curvature) and dominance hierarchy. Finally, we determined whether generalist core hummingbird species are lees dominant in the community. We recorded plant-hummingbird interactions and behavioral dominance of hummingbird species in a temperate forest in Northwestern Mexico (El Palmito, Mexico). We measured flowers’ corolla length and nectar traits and hummingbirds’ weight and bill traits. We recorded 2,272 interactions among 13 hummingbird and 10 plant species. The main driver of plant-hummingbird interactions was species abundance, consistent with the neutrality interaction theory. Hummingbird specialization was related to dominance and bill length, but not to bill curvature of hummingbird species. However, generalist core hummingbird species (species that interact with many plant species) were less dominant. The frequency of interactions between hummingbirds and plants was determined by the abundance of hummingbirds and their flowers, and the dominance of hummingbird species determined the separation of the different modules and specialization. Our study suggests that abundance and feeding behavior may play an important role in North America’s hummingbird-plant networks

Acoustic records of Promops centralis (Thomas, 1915) (Chiroptera, Molossidae) in corn agroecosystems of northwestern Mexico

The Big Crested Mastiff Bat, Promops centralis (Thomas, 1915), is widely distributed from Mexico to South America but has yet to be reported in the state of Sinaloa, Mexico. We collected 122 acoustic recordings of P. centralis from tropical dry forest and agroecosystems in Sinaloa and Sonora for two years (2015 and 2016). We documented a new record for P. centralis outside the known distribution area in northwestern Mexico. Our results reveal that the current P. centralis distribution needs to be reevaluated

Endemic and endangered Short-crested Coquette (Lophornis brachylophus): floral resources and interactions

The Short-crested Coquette (Lophornis brachylophus) is an endangered species endemic to Mexico. Currently, its distribution area is estimated at 53 km². Little to no information exists on its natural history, abundance, and distribution. The purpose of the present study is to describe its food resources, behavior, and interactions with plants and other hummingbirds in addition to its abundance and distribution along an altitudinal gradient. We found that the Short-crested Coquette is sparsely distributed and ranges from tropical sub-deciduous forest to cloud forest. It can also occupy cultivated lands and forests with shade coffee plantations. It moves along an altitudinal gradient following the blooming of its floral resources, similar to other hummingbird species in the study region. It is a generalist, subordinate species that shares its distribution with 14 other hummingbird species. It interacts with some of these hummingbirds and plants in a nested network of interactions with low levels of connectance, visiting 8 of the 23 plant species commonly used by hummingbirds in the area. More in-depth studies on its reproduction and interaction with different plants and important crops in the area are required. The results of the present study can be used to propose programs for the management, conservation, or recovery of the habitats inhabited by the Short-crested Coquette and other hummingbirds