Fire!!

Fire is an integral part of life in the Northern Territory, and particularly in tropical savannas. In fact, tropical savannas are what they are in large part because of fire. Without periodic burns, grasslands with sparse trees would quickly develop into forests.

Our study site is located in a private property near the Coomalie Creek. The land owner conducts regular “cool burns” at the end of the monsoon season in order to simulate a natural fire regime and so that if fire were to start it would not get out of control. These creates a mosaic of burned, recently burned, and unburned habitat, with burned areas and roads both acting as fire breaks if a dry season fire were to sweep through.

Living in the land of fire became a little more familiar to all of us in the past month when a fire that started near Adelaide River (likely started by “weekend warriors”) came up north to our study site, ultimately burning about half of our study area and coming within a kilometer of our house! The day started off as normal: waking up in the dark, eating breakfast in the dark, and heading out into the field  in the dark. I drove up into the middle of the site and got out in order to listen for birds (along with Mitch and Tess) that we would try to catch with mist nets. Kelly also got out to start heading towards the start of one of her occupancy model transects. It was still dark, but the smoke in the air was thick and we could hear the crackling of fire. “Guys, I think that fire is really close,” said Kelly. “Nonsense,” I replied, “It’s just an illusion. I’m sure it’s kilometres away.” “But I can see the flames.” Sure enough, looking through the trees the orange tips of flames were visible. “I’m sure it won’t affect your transect, go ahead and head in the direction” I told Kelly. Kelly headed off in the direction of the fire and we dispersed to listen for birds, but a few minutes later there was a crackling on the radio. “The fire is right here!” said Kelly. We drove down the road to meet up with Kelly and the fire had already burned a good portion of “the horseshoe,” a popular part of the study for wrens and the spot where we saw our first flock as a group. That part of the fire burned out later in the day, but another finger of the fire coming from the south jumped a fire break and came up through the center of the site, burning an area filled with dense gamba grass, an exotic species introduced from Africa that has tremendous fuel load potential. We missed seeing the actual flames because it all happened so fast, but the area that was home to a fair number of the birds that we had banded was completely gone, with only blackened earth and lone silhouettes of eucalypts remaining, some still burned logs, and a few tufts of grass that managed to escape the flames. Only hours after the fire the wrens were active, and we witnessed birds that afternoon and the next morning contact calling persistently in the area of the burn. However, after a day they had all dispersed; some of them we have resighted in adjacent unburned areas and others of them are still MIA, but are sure to be found. By marking the locations where the birds were captured and where we resight them throughout the birds lifetime, we will be able to see not only how the birds respond immediately to fire, but also if they return to their original territories once the grass regrows or if their temporary relocation becomes permanent.

I just realized that I don’t have any photos of the fire or the aftermath, so stayed tuned for some at a later date. For now, here is a picture of the crew in Kakadu with a fire in the distance and of some smoke from a more distant fire (that one wasn’t an illusion) from the airstrip.

50 shades of bright

Although there have been many studies on fairy-wren ecology and behavior during the breeding season, little work has been done when the wrens are not breeding. The peak for RBW breeding here at Coomalie is supposed to be in February, placing our IRES experience right in the middle of the non-breeding season (and in the winter/dry season in the Northern Territory).  As expected, many of the wrens when we arrived were in medium sized flocks rather than the normal breeding season pairs. A fair number of males were spotty–either molting into or out of bright plumage, although since we were unable to catch a large number of birds until July, it is not clear which of their two annual molts they were in. However, it is now clear that in the past few weeks a number of males are molting into their nuptial black and red plumage, which is what is referred to as “bright” plumage as opposed to the “dull” female-like plumage. Other males are in eclipse plumage-still identifiable as males because of a few black feathers here or there and a few red (or orange!) feathers on their backs. It seems that the males are gearing up for breeding, although we don’t know if breeding will happen early this year or if they are simply prepping months in advance. Other studies on congeners have shown that the date that males molt into nuptial plumage is one of the best predictors of male extrapair success, thus being here when the birds are molting is great for getting data!

Adding further evidence that the males are gearing up towards breeding, I saw the first petal display of the year a few days ago. Males looking to show off to potential mates or partners find a nice flower petal or seed that compliments the crimson on their back (in this case the petal was pink) and carry it around to show off to the ladies. Bright male BEY carried around the petal for a good ten minutes before presenting it to a dull bird who took it and flew off with it. Is she going to choose him as a mate or extrapair partner? Only time will tell, although it clearly seems like a little bit of courting is going on during these non-breeding months. BEY was in a flock with at least 3 bright males and one spotty male, and although there was a little bit of kerfuffling between these guys, the wrens were definitely in a mixed flock and not in territories. Over the next couple of weeks I will hopefully be able to keep collecting colorband resighting data to be able to see how associations and relationships between individuals during the nonbreeding season translate into fitness during the breeding season.