My PhD focused on how birds respond to climate change via changes in their morphology. This stemmed from two biogeographical rules: Allen's rule and Bergmann's rule. The rules state that animals tend to be smaller bodied but with bigger appendages in warmer climates, as a way of optimizing their heat loss and retention. These morphological trends have been found to exist across latitudinal gradients in some mammals and birds, thus leading to the speculation that the same trends would exist through time, in response to climatic warming.

One of my thesis chapters reviewed examples of increases in appendage size relative to body size (and thus changing overall shape, hence the term "shape-shifting"). This paper sparked a fair amount of media attention when it was published in Trends in Ecology and Evolution (see Media appearances tab and our article for The Conversation). We then got the opportunity to respond to comment that was published about our paper, to discuss how allometry gets accounted for when evaluating Allen's rule.

I also had the opportunity to write a News and Views article for Nature Climate Change about a paper published by them in 2022, looking at body size decreases in tree swallows.

To investigate shape-shifting, I made use of a 3D scanner to be able to extract surface area measurements of bills (rather than estimates of bill surface area, generated from linear measurements). My second paper focused on using 3D scanners on museum specimens, to ensure the method was repeatable between observers and to understand how manual measurements differed from the 3D scan-based measurements. It was published in Journal of Avian Biology.

My third thesis chapter investigated changes in bill surface area, tarsus length, and body size in Australian birds over the last century. I used the method outlined in the above paper in Journal of Avian Biology to extract morphological measurements from museum specimens of diverse Australian species. We found increases in bill and tarsus size, but decreases in body size, through time across birds. Conversely, we found that all morphological measures decreased in response to short-term hot weather. The paper was published in Global Change Biology, and we published an article in The Conversation about it. 

Along with the above paper in Global Change Biology, I was part of a concurrent project looking at similar questions but in Australian shorebirds, led by Dr Alexandra McQueen. This project found matching results in live-caught birds over 5 decades, finding increases in relative bill size and decreases in body size over time. Importantly, this study also found decreases in all morphological measurements after short-term hot weather. This paper was published in Ecology Letters in their special issue on 'Ecological and Evolutionary Insights from Very Long-Term Studies'.

Discussions with Alex over the years also gave rise to another publication, but this time a Perspective piece. We realised that many in the field were looking at changes in relative trait size using different methods, either correcting for body size by doing a ratio (appendage/body size) or a multiple regression (appendage ~ body size). We tested either method on simulated and real-world data to show how different they can be, and conclude that multiple regression is a more suitable method. This paper was published in Evolutionary Ecology's Special Issue 'Morphological responses to climate change'.