The main question I aim to address is how animals integrate different behavioral, physiological and molecular traits to respond to environmental heterogeneity in an evolutionary framework.

 

1. Research lines 

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I. Integrated responses to global change: Functional genomics, physiological and behavioral traits

 

In recent years the occurrence of unpredictable climatic events linked climate change and human disturbance has dramatically increased. In my current research project, Facing global change: Integrative strategies to cope with life in the Desert, we aim to achieve a broader understanding on the elements involved in how different phenotypes cope with unpredictable events, and environmental variability. Thus, I used an integrative approach, combining the assessment of behavioral strategies, endocrine regulation, and proteomics. The study is carried out in two populations of Rufous-collared sparrows (Zonotrichia capensis) in the Atacama Desert (extremely stable conditions); and in the semiarid Fray Jorge National Park (extremely unstable environment) in central Chile (~1800 km South). In the first population where seasonal fluctuations are much less severe (i.e., lower ambient environmental heterogeneity), birds have lost all seasonality in their life cycles, molting and breeding year-round, and even expressing breeding and molting at the same time, without negative effects on fitness. In contrast, in the seasonal and unpredictable valleys around the Fray Jorge National Park, birds follow a strict separation of LHS across the annual cycle (Fig. 1).

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​​In addition of overlapping breeding and molt, birds in the Atacama Desert exhibit atypical molt patterns, showing complete asynchrony between wings, random molting feather order within a wing, and differential feather retention –possibly for more than two seasons. In addition, we observed low feather quality in comparison with birds in the seasonal Fray Jorge where birds molt faster, and show the common feather replacement patterns for the majority of passerine birds. The secretive behaviors associated with molt which have been widely described, are not found in the Atacama Desert birds, which is most likely associated with the extended molt period.

In terms of endocrine mechanisms, the adrenocorticoidal stress response –assessed as corticosterone levels- and androgen levels followed marked seasonal patterns in the seasonal Fray Jorge, with higher levels during the reproductive season than molt and wintering LHS. In contrast, birds in the Atacama Desert showed attenuated CORT and androgens profiles, even during molt, where birds did not significantly decreased the stress-induced levels of CORT. Considering the catabolic action of glucocorticoids most of birds suppress stress response during molt, avoiding the production of low quality feathers, which we observed in the Atacama Desert. Although we found differences in the proteome of both populations, these differences were not associated with the degree of seasonality experienced by these two populations. In particular, heat shock proteins, associated with stress response, were not positively associated with variations in glucocorticoids.  

         Currently, in my new project entitled “Geographic variation of life cycles in xeric and unpredictable environments: an integrative approach to study coping mechanisms”  I aim to understand how flexible phenotypes are to face unpredictable perturbations. I am assessing the timing and duration of life history stages, molt patterns, and endocrine stress response in a latitudinal gradient spanning 1,800 km, and an altitudinal gradient of 3,500 meters. In addition, in the extremes of my gradient, I am analyzing gene expression associated with the organization of life cycles and stress response. I will also perform a translocation experiment where I will hold birds from the lowlands in Atacama Desert and Fray Jorge populations (the extreme of our gradient) in semi-natural captivity to assess phenotypic flexibility in LHS organization, molt patterns, and gene expression.

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II. Field Cognitive Ecology

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Hummingbird energetic balance is the result of a complex interplay among foraging behaviors, cognitive performance, physiological constraints, and environmental conditions. Thus, they are a particularly interesting group in which to examine the evolution of cognitive performance, investigating the possible selective pressures involved in their development.

Cognitive abilities such as learning and memory are critical for the performance of behavioral traits strongly linked to fitness, such as mating and foraging. These abilities could act as a buffer against environmental unpredictability, via the facilitation of resource exploitation. Hummingbirds are an interesting group in which to examine the link between cognitive performance and these variables considering their high energy demands, diet, ecosystem role, and diversity of environments in which they occur. To answer these questions, I work with free-living individuals in Mediterranean (Chile-California) and tropical environments (Costa Rica). I have developed field-based techniques that allowed me to assess individual differences in memory and learning. I observed the most remarkable spatial memory abilities in dominant males. Based on this experiment, I developed a protocol, to test their ability to match their visits to renewal nectar rates, remembering when the nectar is available. Males were able to match their visits with the nectar schedules, although they preferred the high quality reward, showing they can integrate time, location, and nectar renewal rates. I worked in endocrine assays that allowed me to use cloacal fluid instead of blood, and studied the drivers of aggression.  

 

Also, I have collaborated to study spatial memory in male of long-billed hermits (Phaetornis longirostris, 6 g), a tropical trapliner resident species, where we were interested in the role of cognitive abilities in female choice. We tested spatial memory, and discovered that cognitive performance is as important as bill weapons, a sexually selected trait, and body size to acquire a territory in the lek, which is probably linked to reproductive success. As a team we discovered that cognitive performance is as important as bill weapons, a sexually selected trait, and body size to acquire a territory in tropical hummingbirds. I am currently writing a grant proposal to the integration of molecular, physiological and behavioral traits in hummingbirds in different environments.

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2. Active Research Projects & Collaborations: [or how to put ADHD at work :) ]

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a. Effects of heatwaves on stress response in breeding birds in California

I am currently collaborating with two graduate students at UC Davis who are carrying out projects assessing the effects of heatwaves on growth and provisioning rates in Tree Swallows, Western Bluebirds and Black Phoebes.

 

b. Adapting to Uncertainty: Investigating Genetic and Epigenetic Resilience in Wild Passerine Birds. In collaboration with colleagues of the Uppsala University, Sweden (Dr. Carlos Guerrero-Bosagna, Dr. Fabio Pertille) we are assessing epigenetic modifications of the DNA and their relation to glucocorticoid circulating levels and the timing of life cycles in birds. We are particularly interested in the comparison between birds inhabiting aseasonal, seasonal and unstable environments. 

 

c. Integration of bill weapons and other sexually selected traits in hummingbirds. For over 20 years I have worked with hummingbirds aiming to understand the traits that can buffer environmental variability. I have tested cognitive abilities, energetics and aggression, as well as endocrine regulation of this behavior in free-living hummingbirds. I have carried out these studies in Mediterranean (Chile-California) and tropical environments (Costa Rica). This field season I will be assessing the role of endocrine regulation on sexually selected traits in tropical and Mediterranean hummingbirds. My hummingbird research is carried out in collaboration with colleagues at the Universidad de Costa Rica, and Burke Museum University of Washington.

 

d. Relation between feather growth, glucocorticoids and body condition in Zonotrichia leucophrys. Feather development can be negatively affected by increases in corticosterone, however these effects on feather growth have been less studied. In this project we testing these ideas in migratory and non-migratory subspecies of With-crown Sparrow.

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e. Long term assessment of the effects of a mega-drought on waterbird communities in Central Chile. Since 2005 I have been part of a group of collaborators investigating the effects of rainfall patterns on the richness and abundance of waterfowl species in a network of wetlands in central Chile. Taking advantage of the analysis of satellite images and in-situ avian abundance estimations, we are analyzing if artificial water reservoirs represent a suitable habitat for these communities. Furthermore, we are especially interested in the effect of the drought on migratory species which use coastal natural wetlands as stopovers.

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f. Comparing Native and Exotic Plant Species as Hummingbird Resources in California: The Role of Evolutionary History and Cultivar Selection

In collaboration with the UCD Arboretum, this project investigates how California native and exotic plant species serve as nectar resources for hummingbirds, with a focus on evolutionary compatibility and nectar availability. Hummingbirds are specialized nectarivores native to the Americas, possessing unique digestive enzymes that allow them to efficiently process the high-sucrose nectar typical of many New World plants. In contrast, many exotic ornamentals in California landscapes originate from regions outside the Americas, where nectar-feeding passerines (e.g., sunbirds, honeyeaters) evolved. These birds possess different digestive adaptations, and the plants they co-evolved with often produce nectar with differing sugar compositions and concentrations. Our first objective is to assess whether exotic plants offer nectar that is chemically and energetically suitable for hummingbirds by comparing nectar volume and sugar composition across native and exotic species.

The second component of this study explores the effectiveness of cultivars versus straight native species as hummingbird resources. While cultivars of native plants are widely used in horticulture for their aesthetic appeal—such as more vivid colors, double flowers, or compact forms—these traits may come at the cost of nectar quality or quantity. Since most cultivars have been bred for human preference rather than ecological function, it is unclear whether they provide equivalent nutritional resources for hummingbirds compared to their wild-type counterparts.

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