Yesterday morning Channel 7 Sydney news broadcast live from the Coomalie airstrip! Correspondent Edwina Bartholomew interviewed Richard as well as his friend Nick, owner of a WWII Harvard aircraft. Short features every half hour featured the Nick and the Harvard, Richard and the Willy WWII jeep, the plane-spotting chair (which allows you to recline while holding binoculars, hence it would also be a good bird-spotting chair!), the cricket pitch (which is surrounded by 11 termite mounds—a full team!), and the live milkwood tree growing from the ashes of a Mosquito airplane crash that was burned to celebrate the end of the war. Stay tuned for further blog posts about the WWII history of Coomalie.
Last year in July we had a pretty big uncontrolled burn sweep through the field site, burning almost half of our core study area. However, 10 months later you can’t even tell there was a fire! Check out these photos to see regrowth over the past wet season:
We got three more inches of rain last night, but supposedly a cold front is coming through this weekend…
Within an hour of finding out that I had missed my connecting flight and would be stuck overnight in the Denver airport, the hard drive on my field computer crashed….However, compared to last year (when my hard drive crashed the night before my flight and I experienced a 24 hour flight delay mid-trip), things were looking slightly up—I had a two-day layover at home to visit family during which I was able to get back up and running with a new laptop! (Now I know next year to expect my computer to crash a week before departure and about an 8 hour travel delay….). Fast forwarding beyond those slight logistical hiccups and here I am again at Coomalie! I haven’t had any Tim Tams yet, but I did see a dingo chase a wallaby this morning, and the flying fox shrieks as they return to their roost every morning makes for an authentic Australian wake-up alarm.
The past wet season was one of the driest on record for the area. Although infrequent, the rains have been somewhat prolonged, and on Friday night we got 3 inches of rain! The weather remains hot and humid, making it feel like the wet, but it is forecast to dry out in about a week, and I expect by the time the IRES fellows arrive that I will remember why I packed a sweatshirt and fleece jacket.
The wrens are also slightly behind schedule from what they were doing at this time last year. When I arrived in 2012, the birds were already in small flocks, whereas this year the birds I have seen so far have still been paired up. I have caught a handful of birds and each one has been molting heavily, with the “post-nuptial molt” marking an official beginning to the non-breeding season. Again contradicting last year, when a number of birds retained nuptial red and black plumage throughout the dry, this year I have only seen dull wrens. This means that the timing of our field season should allow us to capture the transition into social flocks, which should give us nice data on the shift in social structure throughout the dry season.
The timing of the pre-nuptial moult in RBWs varies extensively between individuals and populations over a period of approximately 6 months. The lengthy timing of the pre-nuptial moult in RBWs is indicative of phenotypic plasticity—the ability to change phenotype in response to environmental triggers (Price et al. 2003, Coquillard et al. 2012)—that allows organisms to match their phenotype to temporally and spatially heterogeneous environments. Importantly, the pre-nuptial moult date, thought to represent endurance because of the duration of the year that males display nuptial plumage, is the main predictor of fitness for congeners M. cyaneus and M. splendens (Mulder and Magrath 1994, Dunn and Cockburn 1999, Brouwer et al. 2011). But, how do the social and ecological environment affect when individuals complete the pre-nuptial moult?
Social network theory has recently emerged as a valuable tool to understand interactions and associations between individuals (Wey et al. 2008; Sih et al. 2009; Croft et al. 2011), and may be utilized to better understand both qualitative and quantitative interactions between individuals. The application of social network theory to social flocks and changing social organization offers a valuable tool to understanding the effects of social organization on potential fitness.
I used observations and capture records of RBWs on our site to create social networks using Gephi software (Bastian et al. 2009) for two periods: 10 July -8 August 2012 (considered the non-breeding season) and from 1 December-13 January (the pre-breeding season). Individuals are represented by nodes, and interactions are represented by undirected ties (meaning that interactions did not have an initiator or recipient). The degree is defined as the number of ties that an individual has, representing the number of other individuals he interacts with. Node color represents sex and phenotype of the birds.
The non-breeding season was characterized by high connectivity (see Social Network figure below). Average degree was 4.4±2.9 individuals, which did not differ based on sex. However, bright males had a significantly higher degree than dull males in the non-breeding season. During the pre-breeding season, most of the birds were in social pairs. This is reflected in a significantly lower degree (1.6±0.8) than during the non-breeding season. Degree did not differ based on sex or on plumage.
During our work this summer, we will continue to investigate social organization, in addition to collecting data on how the ecological environment may affect social structure. Last year we found a difference in social position between bright and dull males; it will be interesting to see if we can use social organization to predict which males will moult earlier, or if phenotype itself predicts social position. In other species of birds, early social interactions were used to predict fitness later in life, and we hope to determine if there are similar patterns in fairy-wrens.