New paper from @joewoodman.bsky.social DPhil thesis now published. Here, Joe (& 30 friends) use @spibirds.bsky.social to collate data on age structure for 32 Great Tit populations spanning 67 years & involving 130 000 individual birds. Why did we do this? 1/n onlinelibrary.wiley.com/doi/10.1111/... - ThreadSky

sheldonbirds.bsky.social • 4 days ago

New paper from @joewoodman.bsky.social DPhil thesis now published. Here, Joe (& 30 friends) use @spibirds.bsky.social to collate data on age structure for 32 Great Tit populations spanning 67 years & involving 130 000 individual birds. Why did we do this? 1/n
https://onlinelibrary.wiley.com/doi/10.1111/ele.70079

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sheldonbirds.bsky.social•4 days ago

We know variation in age structure can affect population growth rates, but despite evidence for spatial synchrony in population dynamics we don’t know much about the synchrony of age structure across space and what might drive this. 2/n

sheldonbirds.bsky.social•4 days ago

We used breeding age-structure data from 32 popns to ask whether population-specific fluctuations in age structure relate to reproductive & environmental factors that vary at different spatial scales, & if these fluctuations are synchronised by environmental variability. 3/n 📸 @sevans.bsky.social

sheldonbirds.bsky.social•4 days ago

We found that larger average clutch sizes 🥚🥚🥚 have the greatest effect in predicting younger breeding populations the following year, while older populations follow warmer summers and winters but precipitation had no effect 🌧️ 4/n

sheldonbirds.bsky.social•4 days ago

Breeding populations were younger in years that followed a higher beech crop 🌳🌳 – fitting evidence that this increases juvenile survival - and the relationship between masting and age structure was stronger when only assessing populations local to beech data collection. 5/n

sheldonbirds.bsky.social•4 days ago

There is moderate spatial synchrony in age structure, maintained up to ~650km. But, despite their effect on age-structure at the population level, variation in environmental factors doesn’t explain this synchrony, except some synchronising effect of beech masting at local scales. 6/n

sheldonbirds.bsky.social•4 days ago

Other effects (e.g. spatially autocorrelated habitat, predator or prey density) which we could not assess in this study might be driving this synchrony – it would be intriguing to find ways to test their effects. 7/n

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