Thread by @_Marc_Gilles

Our paper (with @LeaGrie) on the functions of #bird #odour is out in Biological Reviews doi.org/10.1111/brv.12…

Don’t have time to read the full paper just yet? Here’s a summary thread 🧵 [1/14]

#olfactory #camouflage #communication #ornithology #avian #olfaction #crypsis

Preen oil is produced by the uropygial gland and birds use it to maintain and waterproof their plumage. But could it have other functions? 🤔 [2/14]

Over the past 20 years, researchers have explored whether preen oil plays a role in chemical defence & communication. Despite this growth in research, many functions of preen oil remain poorly understood 🧐 [3/14]

Preen oil is a major source of the smell of #birds, so it could have olfactory functions! 🤯 [4/14]

Intriguingly, in many species, preen oil composition changes over the year & specifically at the onset of breeding 🤔

Why would the odour of birds change at the start of the breeding season? There are two main hypotheses! [5/14]

Studying seasonal & sex differences in preen oil could help us unravel the functions of preen oil & bird odour!

For example, the changes observed in the preen oil of #shorebirds might protect them & their offspring against predators by reducing odour at the nest 🦊 [6/14]

In contrast, preen oil changes in other species, like #songbirds, may help birds to choose a mate during breeding 🐦 [7/14]

Most studies speculate on functions based on results from a single species. But what if we look at ALL species studied❓ Is there support for either hypothesis❓

@LeaGrie & I compiled ALL studies that investigated seasonal & sex differences in preen oil to find out!😮 [8/14]

We found seasonal differences in 95% of species & sex differences in 47% of species. Most studies were on songbirds & shorebirds [9/14]

We then conducted comparative analyses using data from 59 bird species 🐦🦜🦅🐧🦩🦆🐓

Curious about our analyses? 📊 Find our data & code in the PUB repository (doi.org/10.4119/unibi/…) or my #Github (github.com/marc-gilles) [10/14]

Seasonal differences were more likely in the incubating than non-incubating sex, but only in ground-nesters ➜ support for ✅ olfactory crypsis! [11/14]

Sex differences occured more in species with uniparental than biparental incubation & more during breeding than non-breeding ➜ support for both ✅ olfactory crypsis and ✅ sex semiochemical! [12/14]

The two hypotheses could not be disentangled 🤷 so we make recommendations & testable predictions for future research! 👍 The field of avian chemical #ecology is growing fast, we hope this will help it grow in the right direction 💪 [13/14]

This study was led by @LeaGrie & myself + supported by a fantastic international team of co-authors (@CaspersBarbara, @Beth_macshack, Innes Cuthill & Tamás Székely) 💪 Hooray for #interdisciplinary #collaborative research! 🎉 [14/14]