White-winged Fairywren (dull unknown) by Allison Johnson
Allison and Joe walking through a salt flat. Image by Ian Hoppe.
Purple-backed fairywrens, on the other hand, seem to vary quite dramatically with rainfall! While our data is preliminary and represents only a quick snapshot of the populations, we think some patterns might be emerging. It seems like there may be fewer bright males at sites experiencing lower winter rainfall (sites further to the north along the transect) and that there may be more males than females in these same populations.
Our most striking result however, is for group size. We observed a strong relationship between the average group size of each site we stopped at and the winter rainfall that site experienced in 2018 — sites with low winter rainfall had the largest social groups! This is exactly what we were predicting, previous research has shown that purple-backed fairywrens who have helpers at their nest produce more offspring, so it was exciting to find larger group sizes in harsher environments.
Why might this pattern emerge? It may be beneficial to the helpers to stay in their natal territories or join someone else’s territory when their prospects for rearing young on their own are low or when their survival might be negatively impacted by dispersal (such as in an arid environment), similarly, breeders may benefit from having helpers at their nest to provision young when the habitat quality is low and insects are hard to find, lightening the parental care load they must carry themselves.
Bright male Purple-backed Fairywrens. Image by Allison Johnson.
We hope you find these results as exciting as we do! We can’t wait to start comparing your data coming in from eBird to our transect results and to start examining variation across species. As we’ve already seen from the transect, what happens in one species might not happen in another!
We are already planning our next transect trips for 2019 — this time we hope to compare group sizes and plumage types between the winter and breeding seasons. As the seasons are changing, keep the fairywrens in mind! Let us know what you are seeing! As always, let us know if you have any ideas or question. Get in touch via Facebook or email (fairywrenproject@gmail.com).
Happy birding!
Allison and Joe
