Double Clutchin’ by Brad Kubecka, Graduate Research Assistant
Q: “I’ve been seeing a lot of big broods. Are the birds on their 2nd or 3rd hatch right now?”
A: Well …
First, it is important to distinguish the difference between 2nd, 3rd, and 4th nest attempts and 2nd or 3rd broods (i.e., successful, successive clutches). An average from 2009–present RPQRR data suggest about 12% of radio-collared bobwhite hens attempt a 2nd nest and a small handful attempt a 3rd or even 4th. There is much variation about this estimate for logistic and biological reasons. For example, perhaps a nest is depredated before being found or reproductive vigor is depressed for a particular year. In 2015 nearly one-third of our radio-collared hens attempted > 1 nest, but in 2011 none attempted a 2nd nest (few even attempted 1 nest)
A question of probability
One way to describe the truth to our question lies in probability. Our question now becomes “what is the probability of a hen having 3 successful hatches?” A few parameters we might use to answer this question are 1) proportion of hens that lay a nest, 2) nest success, and 3) proportion of hens that re-nest after successfully hatching a prior clutch. When we calculate this probability, the product is multiplicative. For example, the probability of rolling a 6 on a die is 1/6, but the probability of doing it twice in a row is lower (1 in 36). Likewise, if the national average for bobwhite nest success is 28% (Rollins and Carroll 2001), the odds of having 3 successful nests is much lower (.28 x .28 x .28 = 0.022). Now consider factoring in the proportion of hens that even attempt a 2nd or 3rd nest after a previously successful hatch. And perhaps 20% of hens are killed while nesting. When we keep factoring in all the parameters, we find that the probability of a hen actually having 3 successful nests is very, very low. So where do all the big broods come from?
Putting it all together
We now know 1) not all birds attempt > 1 nest per season, 2) nest success is relatively low, 3) the probability of multiple successful nests is even lower, and 4) as an aside, chick survival is also relatively low. When we see large broods, other dynamics are likely in play. Some of these dynamics such as brood amalgamations have been discussed at length in previous newsletters.
RPQRR Quick Facts for Nests, 2009-16 ( ± SE)
Average Clutch Size: 12.8 ± 0.3
Hatchability (average % of eggs that hatch / clutch): 88%
Nest Success (%): 60.1 ± 3.7.
A New Way to Look at Quail Habitat
It’s called “density gradient modeling.” Think of it as a radar image depicting thunderstorm intensity. In this case being “in the red” is a good thing. Recently John Edwards, a PhD student at Texas A&M University-Kingsville conducted helicopter counts at RPQRR and 3 other area ranches to construct maps illustrating the spatial distribution of bobwhites across the property. The counts at RPQRR are part of a CKWRI research project studying the effects of habitat, climate, and raptors as factors in the quail decline. The map depicted here is a density-gradient map, which uses the covey-detection information provided from the survey such as covey size and location plus additional habitat variables to create a map of bobwhite density across the property. This allows us to evaluate bobwhite density spatially across the landscape. RPQRR’s Brad Kubecka, who is currently pursuing his MS degree at TAMU-K under Dr. Hernandez and me, will be analyzing similar data to better understand how habitat factors (e.g., brush density) affects such density-gradients over the course of the past seven years. Stay tuned; neat stuff.
Addressing the Eyeworm Threat in Bobwhite Quail
Addressing the Eyeworm Threat in Bobwhite Quail from Dale Rollins on Vimeo.
- Bruno, A., A. M. Fedynich, A. Smith-Herron, and D. Rollins. 2015. Pathological response of northern bobwhites to Oxyspirura petrowi infections. Journal of Parasitology: In-Press.
- Dunham,N. R., L. A. Soliz, A. Brightman, D. Rollins, A. M. Fedynich, and R. J. Kendall. 2015. Live eyeworm (Oxyspirura petrowi) extraction, in vitro culture, and transfer for experimental studies. Journal of Parasitology: 101:98-101.
- Dunham, N. R., L. A. Soliz, A.M. Fedynich, D. Rollins and R. J. Kendall. 2014.
Evidence of an Oxyspirura petrowi epizootic in northern bobwhites (Colinus virginianus), Texas, USA. Journal of Wildlife Diseases 50:552-558.
- L Xiang, F Guo, H Zhang, L LaCoste, D Rollins, A Bruno, AM Fedynich, and G. Zhu. 2013. Gene discovery, evolutionary affinity and molecular detection of Oxyspirura petrowi, an eye worm parasite of game birds. BMC Microbiology 13:233.
Operation Idiopathic Decline: Texas Tech Researchers Discover Blood-Sucking Parasite Epidemic in Wild Quail
Operation Idiopathic Decline confirmed that bobwhites across the Rolling Plains of Tx and OK are heavily infested with eyeworms and cecal worms. Additional research is underway at the Tx Institute of Environmental and Human Health at Texas Tech University to assess how eyeworms impact flying and foraging ability of quail, and towards the development of a method to treat wild quail for these two roundworms. Here the lead investigator on the project, Dr. Ron Kendall, provides an update.
Operation Idiopathic Decline: Search for the Smoking Gun
The role that disease and parasites may play in quail dynamics has been largely ignored since the 1920s. After the (in our opinion) inexplicable decline of quail in the Rolling Plains, the Board of RPQRF “got serious” about disease and funded a comprehensive project dubbed “Operation Idiopathic Decline.” Currently (as of Feb 2014), the RPQRF has invested $3.4 million into this ground-breaking study of disease and parasites. This webisode explains OID in more depth.