Summary: A new study finds that female mountain chickadees in socially monogamous pairs frequently mate outside their pair bonds with males that demonstrate superior spatial memory and learning. Researchers tracked individual birds using automated “smart” feeder arrays to measure spatial errors and combined these data with genetic paternity analysis over three breeding seasons. They report that 70% of monitored nests contained at least one extra-pair chick, and most extra-pair offspring were sired by males with top-tier spatial cognition.
High-performing males fathered as many as six to seven extra-pair young per year and tended to produce heavier fledglings that are more likely to survive. Notably, females that scored lower on spatial cognition tests were more likely to have extra-pair young in their nests, suggesting a deliberate mating strategy to secure heritable advantages for their offspring.
Key Facts
- Intellectual mate choice: Females in socially monogamous mountain chickadee pairs actively seek extra-pair mates with stronger spatial learning and memory than their social partner.
- “Smart” feeder assessment: Automated feeder arrays recorded how many location mistakes each tagged bird made; fewer errors indicated better spatial cognition.
- High extra-pair incidence: Over three breeding seasons, roughly 70% of nests included extra-pair young, comprising about one-third of sampled offspring.
- Top sires: Males with the best spatial memory sired the largest numbers of extra-pair young annually, without apparent loss of paternity or chick quality in their own nests.
- Compensatory mating by females: Females with lower spatial-cognition scores were more likely to pursue extra-pair copulations, presumably to improve offspring fitness.
- Better chick condition: Males with superior spatial abilities produced heavier fledglings on average, increasing offspring survival prospects.
Source: eLife (Reviewed Preprint)
Female chickadees in monogamous systems actively seek males with stronger spatial cognition, new research shows.
Extra-pair copulations occur across many animal species, including species that form socially monogamous pairs. These matings can yield genetic benefits by increasing offspring fitness. Understanding why females mate with multiple males and how those choices affect survival and reproduction is central to evolutionary biology.
Lead author Carrie Branch, Assistant Professor at Western University, explains that females are often choosier due to their greater reproductive investment and therefore seek mates who will increase the likelihood of successful offspring, reliable parental care, and beneficial heritable traits. Spatial cognition—skills for learning and remembering locations—helps animals survive in variable environments and has the potential to be inherited and shaped by selection. Until now, evidence that females choose mates based on cognitive ability in the wild has been limited.
To investigate, researchers studied wild North American mountain chickadees (Poecile gambeli), a nonmigratory, food-caching species that depends heavily on spatial memory to locate stored seeds. The team installed automated feeder arrays that were configured so each tagged bird could obtain a reward from only one specific feeder slot. By recording radio-frequency identification (RFID) tags and tracking landing mistakes before a bird reached its designated reward, the scientists quantified each individual’s spatial learning errors as a measure of cognitive performance.
Genetic paternity was determined across three breeding seasons and compared with the cognitive scores of both social and extra-pair males. The study found that about one-third of offspring sampled were sired by extra-pair males and that 70% of nests contained at least one extra-pair chick. Males with fewer spatial errors—the better learners and memorizers—sired more extra-pair young. The best-performing males could sire six to seven extra-pair chicks per year. Male age did not predict extra-pair success.
Males who sired extra-pair young appeared not to lose fitness at home: there were no differences in the number of chicks or short-term chick mass between extra-pair sires and the social males they cuckolded. However, males with stronger spatial cognition tended to rear heavier offspring overall, a trait linked to higher survival into the breeding population.
Crucially, extra-pair sires generally had better spatial cognition than the social males they cuckolded, independent of age. This pattern supports the idea that females prefer males with superior spatial abilities. At the same time, the likelihood of a female having extra-pair young was not driven by her mate’s cognitive score; instead, females who performed worse on spatial tests were more likely to have extra-pair offspring. This suggests that some females may actively seek higher-quality cognitive genes to offset their own limitations.
Senior author Vladimir Pravosudov, Professor of Biology, emphasizes that these findings indicate female mate choice can drive the evolution of spatial cognition in species that rely on caching and memory. Males with better spatial recall sire more offspring and produce fitter fledglings, consistent with sexual selection favoring cognitive traits and with the “good genes” hypothesis that females gain indirect genetic benefits through extra-pair mating.
Key Questions Answered:
A: Mountain chickadees are nonmigratory residents in harsh, variable environments and cache thousands of food items across wide areas. To survive winter, individuals must accurately remember the locations of many hidden seeds. Poor spatial memory directly increases the risk of starvation, so spatial cognitive ability is tightly linked to survival.
A: The team used automated “smart” feeder arrays and RFID tags. For each tagged bird, only one feeder slot would unlock and deliver a sunflower seed. The number of incorrect landings before reaching the rewarding slot provided a precise, error-based metric of spatial learning and memory.
A: The study shows the probability of extra-pair young in a nest was linked to the female’s own cognitive performance rather than the social male’s. Females with weaker spatial memory appear to seek extra-pair mates with superior cognition, effectively hedging against passing on poorer spatial traits to their offspring.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The original journal paper was reviewed in full.
- Additional context was provided by staff editors.
About this research
Author: Emily Packer (eLife)
Source: eLife (Reviewed Preprint)
Contact: Emily Packer – eLife
Image credit: Vladimir Pravosudov (CC BY 4.0)
Original research: Male chickadees with better spatial cognition sire more extra-pair young. Branch CL et al., eLife. DOI: 10.7554/eLife.110905.1
Abstract
Male chickadees with better spatial cognition sire more extra-pair young
Across animal taxa, females often mate with more than one male even where social monogamy exists. These extra-pair copulations can enhance female fitness through genetic and other benefits. North American mountain chickadees are a suitable system to examine sexual selection via extra-pair paternity because they are nonmigratory, rely on spatial cognition to recover cached food, and show heritable variation in spatial ability linked to survival.
This study quantified extra-pair paternity and compared spatial abilities of extra-pair males with the social males they cuckolded. Results show that males with better spatial cognition sire more extra-pair young and produce heavier offspring in their own nests. Extra-pair sires also had significantly better spatial cognition than the social males they cuckolded. These findings suggest sexual selection contributes to the evolution of spatial cognition in food-caching chickadees, supporting the good-genes hypothesis that females gain indirect genetic benefits through extra-pair mating.