Biology subjects

Shizuka, D.

Publications and source records attributed to Shizuka, D..

6 recordsLinked to original sources

bioRxiv2026

Individual-level social associations and social information use predict foraging success in winter mixed-species flocks

The acquisition of social information to improve foraging efficiency is considered one of the primary drivers of mixed-species flocks (MSFs). This flow of social information occurs among individuals of multiple species, but analyses of MSFs at the level of species fail to capture the nuances of this dynamic. We investigated how individual-level social associations in North American MSFs impact discovery of novel feeders presented alongside vocal cues. We used radio-frequency identification (RFID) data loggers to track arrivals of individually tagged black-capped chickadees (Poecile atricapillus), white-breasted nuthatches (Sitta carolinensis), and downy woodpeckers (Dryobates pubescens) at fixed feeders, and during novel feeder trials paired with chickadee, nuthatch, or white noise playbacks. For chickadees, a higher number of total associations and conspecific playbacks improved novel feeder discovery. The foraging benefits in nuthatches and woodpeckers were predicted by their individual-level associations with chickadees and these benefits only manifested during chickadee playbacks. We demonstrate that the advantages of mixed-species flocking are not uniformly distributed across species; rather, they are contingent upon individually maintained social associations and the presence of social information. These findings highlight the necessity of quantifying individual variation to accurately assess the evolutionary drivers and fitness consequences of species interactions.

animal behavior and cognition↗

bioRxiv2025

Dynamic membership drives long-term persistence of sparrow winter social communities

Social groups range from highly stable to highly dynamic over extended periods. Demographic factors like individual lifespans and rates of births, deaths, immigration, and emigration in a population can strongly impact group stability and persistence over time. Highly stable long-term groups are often driven by long-lived core individuals that maintain relationships, kin-structure, or high philopatry. In opposition, fluid groups of individuals that associate repeatedly, called social communities, can persist in populations that have high turnover, lack kin structure, and exhibit high fission-fusion dynamics. However, we lack an understanding of how animal social communities persist amidst highly dynamic membership. We investigated the drivers of persistence of social communities in a winter population of migratory golden-crowned sparrows over 12 years. Sparrows frequently flock with the same individuals over the entire winter, forming social communities that are identified from discrete clusters within a social network. Long-term community membership was highly dynamic due to high annual turnover and the relatively short lifespans of individuals. However, the social fidelity of returning members and recruitment of new members between consecutive years resulted in communities that persisted for multiple years, even when there was a complete turnover of members over time. Our results indicate that groups can persist with consistent short-term membership, overlapping generations, and turnover with balanced rates of recruitment and loss. This dynamic stability of individual membership may be a universal feature of large, long-term groups found in many social systems, from animal societies with fission-fusion dynamics to networks of human collaboration.

animal behavior and cognition↗

bioRxiv2022

Ecological flexibility and selectivity in mixed-species flock participation in birds

Mixed-species groups are hypothesized to allow animals to minimize competitive interactions and maximize facilitative interactions. Individuals participation in mixed-species groups may reduce rates of competition and increase the social information available about predators or food availability. Behavioral plasticity may further increase these benefits as plastic species alter their rates of niche overlap with group mates. We investigate two axes of behavioral plasticity that may modulate how species interact with group mates in mixed-species groups--flexibility and selectivity. Specifically, we assess avian species patterns of selective preferences for participation in flocks of certain strata and whether behavioral flexibility in foraging strata corresponds with the foraging strata of flock mates. All species in our study maintained or increased their foraging strata overlap with flock mates, supporting the hypothesis that facilitation plays an important role in flock formation. Notably, the methods that species used varied: some species moved closer to flock mates via flexibly matching their flock mates behavior, some showed selectivity for flocks of certain stratums, and others did both. Ultimately, we show that species balance facilitative and competitive interactions with flock mates via multiple methods and that consideration of behavioral plasticity is integral to understanding the nuances of mixed-species flock interactions.

animal behavior and cognition↗

bioRxiv2021

Social migratory connectivity: do birds that socialize in winter breed together?

Researching the complete life cycles of migratory animals is essential for understanding conservation and population dynamics. Many studies focus on the breeding season, but surviving winter is equally important. Living in groups during winter can play a vital role as social connections within groups can provide many benefits such as protection from predators and increased access to resources. However, it is often unknown how social connections change across seasons in migratory animals. We focus on social connections in a migratory bird and ask whether social connections in winter continue during breeding. Golden-crowned sparrows have distinct, stable winter communities which include both site and group fidelity across years: birds almost always rejoin the same social community each year. If these birds have social connectivity across migration, we would expect individuals that associate in winter would also associate together on their breeding grounds. Our small-scale GPS tagging study combined with intensive social behavior data revealed that sparrows in the same tightly-knit winter community migrated to highly disparate locations during summer, showing that social connections in winter do not continue in summer. This suggests that golden-crowned sparrows have entirely separate social structures across seasons and that long-term social memories allow them to reform stable groups each winter.

animal behavior and cognition↗

bioRxiv2019

Juvenile rank acquisition influences fitness independent of adult rank

Social rank has been identified as a significant determinant of fitness in a variety of species. The importance of social rank suggests that the process by which juveniles come to establish their position in the social hierarchy is a critical component of social development. Here, we use the highly predictable process of rank acquisition in spotted hyenas to study the consequences of variation in rank acquisition in early life. In spotted hyenas, rank is inherited through a learning process called maternal rank inheritance. This pattern is highly predictable: ~80% of juveniles acquire the exact rank predicted by the rules of maternal rank inheritance. This predictable nature of rank acquisition in these societies allows the process of rank acquisition to be studied independently from the ultimate rank that each juvenile attains. In this study, we use a novel application of the Elo-rating method to calculate each juveniles deviation from expected pattern of maternal rank inheritance during development. Despite variability in rank acquisition in juveniles, most of these juveniles come to attain the exact rank expected of them according to the rules of maternal rank inheritance. Nevertheless, we find that transient variation in rank acquisition in early life predicts long term fitness consequences for these individuals: juveniles underperforming their expected ranks show reduced survival and lower lifetime reproductive success than better-performing peers. Finally, we present evidence that this variability in rank acquisition in early life represents a source of early life adversity, and that multiple sources of early life adversity have cumulative, but not compounding, effects on fitness.

animal behavior and cognition↗

bioRxiv2019

The role of early acoustic experience in song discrimination

Oscine songbirds are an ideal system for investigating how early experience affects behavior. Young songbirds face a challenging task: how to recognize and selectively learn only their own species song, often during a time-limited window. Because birds are capable of hearing birdsong very early in life, early exposure to song could plausibly affect recognition of appropriate models; however, this idea conflicts with the traditional view that song learning occurs only after a bird leaves the nest. Thus, it remains unknown whether natural variation in acoustic exposure prior to song learning affects the template for recognition. In a population where sister species, golden-crowned and white-crowned sparrows, breed syntopically, we found that nestlings discriminate between heterospecific and conspecific song playbacks prior to the onset of song memorization. We then asked whether natural exposure to more frequent or louder heterospecific song explained any variation in golden-crowned nestling response to heterospecific song playbacks. We characterized the amount of each species song audible in golden-crowned sparrow nests and showed that even in a relatively small area, the ratio of heterospecific to conspecific song exposure varies widely. However, although many songbirds hear and respond to acoustic signals before fledging, golden-crowned sparrow nestlings that heard different amounts of heterospecific song did not behave differently in response to heterospecific playbacks. This study provides the first evidence that song discrimination at the onset of song learning is robust to the presence of closely related heterospecifics in nature, which may be an important adaptation in sympatry between potentially interbreeding taxa.

animal behavior and cognition↗