A new trophic specialization buffers a top predator against climate-driven resource instability

Intraspecific phenotypic variability is key to respond to environmental changes and anomalies. However, documenting the emergence of behavioral diversification in natural populations has remained elusive due to the difficulty of observing such phenomenon at the right time and place. Here, we investigated how the emergence of a new trophic strategy in a population subjected to high fluctuations in the availability of its main trophic resource (migrating songbirds) affected the breeding performance, population structure, and population fitness of a specialized color polymorphic predator, the Eleonora's falcon from the Canary Islands. Using long-term data (2007-2022), we found that the exploitation of an alternative prey (a local petrel species) was associated with the growth of a previously residual falcon colony. Pairs in this colony laid earlier and raised more fledglings than in the other established colonies. The specialization on petreles increased over time, independently of annual ..., The Eleonora's falcon population from the Canary Islands was intensively monitored during July-October 2007-2022. Every year and for each nest-site, we recorded the color morph of both parents using a spotting scope.We visited nests (range = 73-113 nests/year) on at least 2 occasions each year, first to quantify clutch size, and posteriorly to determine the final number of fledged offspring. Laying date (where 1 = July 1st) was calculated by substracting 30 days (the duration of the incubation period) to the hatching date of the older chick within a brood, which was calculated after measuring nestling wing length to estimate their age using the formula provided by Ristow and Wink (2004).The number of fledglings was estimated as the final number of fledged offspring from each nest. Mean annual productivity of the population was estimated as the number of fledglings divided by the number of breeding pairs monitored. We recorded the number of petrels hunted by quantifing the number of inta..., , # Gangoso, L., Viana, D.S., Merchán, M., Figuerola, J. 2024. Data from: A new trophic specialization buffers a top predator against climate-driven resource instability. Behavioral Ecology.

## Description of the data and file structure

Data used is included in two tab delimited txt files: Dataset_petrel and Winds_daily_Sep_2007-2022.

1. Dataset_petrel was used to analyze 1) whether the number of petrels hunted by male Eleonora’s falcons throughout the breeding period is associated with their color morph and the breeding colony, 2) whether the exploitation of an alternative food resource (i.e., petrels) is associated with variation in the laying date, and 3) whether variation in productivity is related to the number of seabirds consumed (petrels) and/or laying date.
The dataset contains 9 columns:

1. **nest**: nest ID
2. **petrel_num**: number of petrels recorded in each nest site
3. **colony**: name of the breeding colony where the nest was located (C = Caldera, R = Rapal...