When I was little, I wanted to be David Attenborough, but here I am at 35 hanging out in the bush and collecting bird sperm samples. I feel like I owe everyone (including my younger self) an explanation.
An interesting career choice
My mum doesn’t like to tell people what I do. She generally states that I work in bird conservation and allows me to remain a mysterious avian Jane Goodall figure in people’s minds. What my mum refuses to tell people is that, after several years of studying and a hard-earned PhD, my current research involves sampling sperm from male birds and checking it out under a microscope to see how fast it’s swimming. And I love it.
When I talk to people about my research, there are several questions that I understandably, routinely get asked. I have collected them here along with the answers. Enjoy!
Why do I study bird sperm?
My work involves figuring out what happens to the genetics of populations when they get very small. Typically this leads to low genetic diversity and increased mating between relatives (inbreeding). Currently, my research specifically focuses on how inbreeding might be affecting male fertility in New Zealand birds. We know that, in groups like mammals, insects, and plants, inbreeding causes males to fire blanks. But no-one has really investigated whether the same is true for birds.
If inbreeding does lead to dodgy sperm, it could be bad news for New Zealand’s birds, many of which have experienced drastic reductions in population size thanks to introduced mammals and habitat destruction. So, as part of my Marsden-funded research program, I visit remote islands and predator-free sanctuaries with my specially designed mobile sperm lab and check up on the sperm quality of, in particular, South Island robins and hihi (stitchbirds). Here’s a handy video to explain a little bit more about my work.
How do you get sperm from birds?
Ah, the classic question that usually gets asked within minutes of telling people what I do. It’s actually pretty simple. Male birds in the majority of species do not have a penis. Instead, both males and females have a cloaca – a single opening for both reproduction and excreting waste. Fun fact: cloaca comes from the Latin for sewer and Cloacina was the roman goddess of the sewage system.
Anyhow, in male passerine birds, the area round the cloaca becomes quite swollen during mating season. This swelling acts as a storage area for semen prior to mating. We can use a technique called cloacal massage to cause a small amount of semen to pool on the surface of the cloacal swelling and then collect it.
What do you measure to check the sperm quality?
We look at two things to judge the quality of a bird sperm sample: swimming speed and morphology. Swimming speed is just that – how fast do the sperm swim around? Morphology refers to the length of the sperm and each of its component parts (the head, the midpiece, and the tail) and also what proportion of the sperm are abnormal (two heads, missing tails etc…). It’s generally agreed that faster sperm are better, and that longer sperm are faster (although there’s still a bit of debate about that).
What we can’t look at is sperm count – how many sperm are in the sample. That’s because the samples we get through cloacal massage are not a true ejaculate. It’s not an accurate representation of how many sperm we would see allocated to a real ejaculate, so this would be an unfair measure.
What do you need to measure bird sperm quality in the wild?
Quite a lot of heavy, bulky equipment, as everyone who’d helped me lug my gear around remote, challenging locations will testify. We can measure sperm morphology back at the lab in Dunedin. Swimming speed, however, has to be measured there and then, right after collection or the sperm will die. And dead sperm are notoriously poor swimmers. There are several challenges here. We need gear to track the sperm. We need to keep the sperm at constant temperature or they’ll die. And we need electricity to run all our gear on.
To solve these issues, I designed a mobile sperm lab that I can take pretty much anywhere. It consists of a tent containing a microscope with a camera on top, connected to a laptop that runs sperm tracking software. To keep the semen warm, we have a slide warmer on the microscope, a simple, but effective, Tupperware box with a reptile heatpad inside and, the pièce de résistance, a specially designed in-bra sperm tube holder that I wear to keep samples warm against my skin. All the equipment runs off a small petrol generator that we can take with us wherever we go.
Do the birds enjoy it?
Almost certainly not. But we try and make it as stress-free as possible for them and keep handling time as low as possible.
So, there you have it – everything you wanted to know (or didn’t even know you wanted to know) about bird sperm research. If you have any other questions about what I do, please post them in the comments box. Sorry, mum, the cat is well and truly out of the bag now…