Esteban Fernandez-Juricic Lab

at Purdue University





Research Interests


The lab is currently focused on two main research areas (read more details below):

- The evolution of visual systems and antipredator and foraging behaviors in birds.

- Strategies to solve human-wildlife interactions in protected areas, airports, and urbanized landscapes.

We follow different methodological approaches to address these topics.

We also have broad interests in behavioral ecology (e.g., social behavior, antipredator behavior), sensory biology (e.g., visual and acoustic communication), animal ecology (e.g., patterns and processes underlying the spatial and temporal distribution of animal populations and communities), and conservation ecology (e.g., endangered species). We welcome students with various research as our lab is highly inter-disciplinary. 


Research area I: The evolution of visual systems and antipredator and foraging behavior in birds


Information provides fitness benefits to organisms because it allows them to assess alternative environmental conditions (relative to food, predators, mates, etc.) before making decisions that will affect their survival and reproduction. For visually oriented vertebrates information is usually obtained through the eyes, which are optical devices that capture and produce an image of the environment where information extraction begins. Birds show a remarkably high inter-specific variability in eye form, shape, optical design, and position in the skull, which leads to different types of visual systems.

A central question is what is the relative role of anti-predator and food finding behaviors in explaining specializations of avian eyes. This is a relevant evolutionary problem because visual systems specialized in a particular type of prey could constrain the ability to obtain visual information about predation. This creates a potential trade-off in gathering information relevant to different fitness components that is poorly understood, because of the scarcity of comparative data on the different elements of the avian visual systems.



We are interested in understanding the mechanisms birds use to gather information that is relevant for fitness (anti-predator scanning, foraging, mate choice) from both physiological and behavioral perspectives. To that end, we study how some visual properties (visual field configuration, visual acuity, variations in the density of photoreceptors and ganglion cells across the retina, sensitivity of visual pigments) influence scanning behavior in different ecological contexts. We assess these visual-behavior relationships in a wide variety of bird species because ultimately we seek to understand the evolution of mechanisms of visual information use in species with different life-histories (e.g., solitary vs. social species, species that live in open vs. closed habitats, etc.).  


Main contributions (for more details see our papers)

(I) Incorporating inter-specific differences in the configuration of visual fields into classic social foraging models (e.g., producer-scrounger) affects qualitatively and quantitatively their predictions. This suggests that empirical studies should test assumptions as to how model organisms gather visual cues (Trends in Ecology and Evolution 19: 25-31).

(II) Coordination of vigilance in foraging groups has been proposed as a mechanism to reduce the time allocated to visual monitoring and to increase the time spent foraging, which would benefit exploitation of resources in groups. However, coordinated vigilance is favored only when animals have a low probability of detecting predators when head-down (e.g., narrow visual fields), but a high probability of being warned when another member of the group detects a predator (e.g., alarm calls). For other combinations of personal and social information, coordinated vigilance has little value and may even have a negative value, which supports the lack of empirical support for this vigilance pattern in loose foraging aggregations (Behavioral Ecology 15: 898-906).

(III) The effects of the distance between group mates on individual scanning and foraging strategies are similar to those of group size variations in foraging aggregations, which suggest that both factors may be affecting the ‘group-size’ effect simultaneously (Behavioral Ecology 15: 371-379).

(IV) Information about conspecific's behavior can be gathered from head-down postures, contrary to the assumptions of many theoretical models (Animal Behaviour 69: 73-81). This is due to the wider visual fields found in many social foraging species (Ibis 150: 779-787). 

(V) Individuals are sensitive to differences in the behavior of conspecifics foraging in groups. The intensity of this response increases with the number of conspecifics behaving in a particular way (e.g., an increasing proportion of time scanning or foraging), and decreases with the distance between neighbors due to a reduction in visual contrast and resolution (Behavioral Ecology and Sociobiology 55: 502-511).

(VI) High light intensity can negatively affect the ability of individuals to gather visual information about predator attacks due to glare effects. Individuals foraging in sunlit patches delay their speed to react to a predator attack in relation to individuals in shaded areas (Animal Behaviour 74: 1381-1390). This effect could vary the suitability of foraging patches depending on light conditions.

(VII) We have developed a system to study the transmission of social information in flocks by building bird robots with skins. Live animals do react to changes in the behavior of robots, and the responses are similar to those given to live conspecifics (Animal Behaviour 71: 901-911). This technique opens up new opportunities to study the mechanisms implicated in the transmission of visual social information in groups.

(VIII) The probabilities of predator detection are lower in species with lower visual acuity, with a decrease from 90% to 35% over 40 meters, in relation to species with higher visual acuity (Behavioral Ecology 20: 936-945).

(IX) Species foraging on the ground tend to have relatively fewer retinal specializations that tree foragers. However, ground foragers show variations in the size of the area centralis (area with high concentration of photoreceptors and retinal ganglion cells) that are negatively associated with eye size (Brain, Behavior & Evolution, in press).

(X) Species of corvids that manipulate tools have wider binocular visual fields and a greater degree of eye movements probably to control visually the position of the tool in the frontal part of the head (in revision).   



Research area II: Strategies to solve human-wildlife interactions in protected areas, airports, and urbanized landscapes  


More than 50% of the human population now lives in cities and suburban areas. Urban sprawl has increased the chances of humans interacting with wildlife under different scenarios. For instance, urbanization increases fragmentation effects, which reduces the suitability of remaining habitat fragments for wildlife. Recreational activities are increasing in areas of conservation concern (e.g., hot-spots), which may increase human disturbance effects, reducing the ability of wildlife to use and persist in protected areas. Airports provide habitat for many bird species; however, they also increase substantially the chances bird-aircraft collisions or bird strikes, like the one that happened in the Hudson River in January 2009. Bird strikes causes economic losses to the aviation industry (approximately 1.2 Billion US$ annually) and the potential loss of lives.  

The tolerance of different bird species to humans appears to be related to the distance at which they detect disturbance. The implication is that to reduce the rate of human-wildlife interactions different strategies may be necessary depending on the type of human activity. Within protected areas, it is important to reduce the chances of wildlife detecting recreationists to minimize disturbance; however, in airports, it is better to increase the chances of wildlife detecting aircraft to enhance avoidance behaviors and minimize bird-aircraft collisions. 



We are interested in three main topics. First, understanding the physiological and ecological factors accounting for the inter-specific variability in detection windows (areas surrounding an individual where the probabilities of detecting tourists increase) to better estimate buffer areas to protect wildlife. Second, establishing the role of habituation and sensitization in the responses of wildlife to different types of human activities. Third, determining suitable management strategies that promote co-existence between wildlife and humans in protected areas and airports, particularly taking into consideration endangered and threatened species.


Main contributions (for more details see our papers)

(I) Human disturbance can interact with forest fragmentation causing synergistic effects at the landscape scale (Condor 102:247-255).

(II) Managing human-wildlife interactions in protected areas requires proximate and ultimate studies. First, we should understand the proximate behavioral mechanisms by which different species respond to recreational activities, and the population level consequences of these interactions. Second, this multi-species level approach should also identify the natural and life-history factors explaining the variability in tolerance to human disturbance and proneness to extinction across species (Conservation Biology 18: 1175-1177).  

(III) We put forward a mechanism to predict human-wildlife interactions based on the relationships between the frequency of human visitation and the frequency of resource use (e.g., foraging, breeding, roosting, etc.) by wildlife (resource-use disturbance trade-off hypothesis). This hypothesis argues that thresholds in the intensity and pattern (both spatial and temporal) of human activity exist below which animals can continue to meet their feeding and breeding requirements, and above which the availability of resources to animals is diminished, thereby reducing the carrying capacity and the suitability of disturbed areas for wildlife (Condor 102:247-255; Oecologia 131:269-278).

(IV) The resource-use disturbance trade-off hypothesis has been successfully tested through observational and manipulative approaches in birds (Condor 105: 316-326) and amphibians (Biological Conservation 123: 1-9).

(V) We developed new spatial and temporal indicators of wildlife tolerance to human disturbance, such as detection distance and time to resume pre-disturbance activities, that help estimate buffer areas that better represent the ecological requirements of different species (Environmental Conservation 28:263-269; Biological Conservation 117: 407-416; Biological Conservation 125: 225-235).

(VI) In a comprehensive theoretical and comparative study, we found that detection distance is the main factor affecting bird inter-specific responses to human disturbance. The implication of this finding is that the same levels of human visitation may affect species in different ways depending on the ability of each species to detect visually the presence of people. Detection distances are related to body mass, controlling for phylogenetic effects; thus, larger species tend to have greater detection distances, and as a result are more sensitive to recreational activities (Journal of Applied Ecology 42: 943-953).

(VII) We have developed a spatially-explicit individually-based simulation that predicts habitat selection and population abundance of species with different degrees of tolerance to human disturbance (Journal of Applied Ecology 42: 943-953; Ecological Complexity 6: 113-134). This simulation allows the user to manipulate both the spatial and temporal distribution of recreational activities (e.g., number and arrangement of pathways, visitation load per pathway, etc.), and the ecology and behavior of different species through cellular-automata approaches. Furthermore, the output of the simulation is habitat-specific because it uses GIS technology, and species-specific because the simulation uses certain biological parameters that need to be estimated from the target species through standardized field protocols. This simulation is intended as one of many tools to help managers assess some ecological consequences of variations in recreational activity levels

(VIII) We have done work on endangered species by developing novel tools to survey individuals using vocalizations instead of catching them (and generating unnecessary levels of stress) (Auk 126: 89-99), and establishing buffer areas for the protection of individuals that have no alternative habitats to use (Avian Conservation and Ecology 4(2): 1).

(IX) We have found that lights can enhance the detection of approaching objects in different bird species (Animal Behaviour 77: 673-684). This has important management implications, as aircraft can be equipped with lighting systems that can be reduce the frequency of bird strikes and make flying safer. 





Last update September 19, 2015