Another nice write-up of our review paper by one of my favorite SciComm outlets, IFLScience!
Check it out here: http://www.iflscience.com/plants-and-animals/jays-and-crows-help-forests-grow-emb-feb-3-2300-gmt
Chris Intagliata, a journalist with Scientific American and PRI's Science Friday, interviewed me for this podcast about our review paper on seed dispersal by scatter-hoarding corvids. He provides a very nice summary of the key points of the paper!
Check it out:
New Oecologia paper: How within-year variation in valley oak acorn crops affects seed predation and dispersal
In our newest paper, which was just published in the journal Oecologia, we investigated how within-year variation of valley oak (Quercus lobata) acorn crops affect the acorn foraging and dispersal behavior of western scrub-jays (Aphelocoma californica) and acorn woodpeckers (Melanerpes formicivorus) at the Hastings Natural History Reserve. We selected 37 trees with different acorn crops and observed them several times from September to December. After estimating the acorn crop by counting all acorns two observers can see within 15 seconds, the tree was observed for an hour. During that hour, each visit by a bird or other animal was recorded, and we noted the fate of all the acorns they handled. Our analysis of almost 200 hours of observation revealed that in trees with large acorn crops, scrub-jays took a larger proportion of acorns (compared to the acorn woodpeckers) than in trees with smaller crops. This is likely due to the different spatial scales over which each species optimize their foraging. Jays don't spend much time defending territories during the non-breeding season, while the acorn woodpeckers defend nesting and acorn-storage trees year-round. Because the jays hide acorns in the ground rather than sticking them in the bark of trees like the woodpeckers do, they provide much higher quality seed dispersal. The trees with large crops thus have higher dispersal-related fitness benefits than trees with smaller crops. Our results also hint at the proximate mechanism by which masting trees benefit from the annual variation in acorn crops.
Pesendorfer, MB & Koenig WD (2016) The effect of within-year variation in acorn crop size on seed harvesting behavior by avian hoarders. Oecologia (doi:10.1007/s00442-016-3557-x) link: http://link.springer.com/article/10.1007/s00442-016-3557-x
Oak-a-holics rejoice! The proceedings of the 7th Oak Symposium in Visalia have just been published. The symposium was held in November 2014 and featured talks by researchers and managers that approach oaks from a variety of angles and methodologies. Among others, Walt Koenig and I also contributed papers. Walt's paper was called "Acorns and Acorn Woodpeckers: Ups and Downs in a Long-Term Relationship" and, while I talked about using ecosystem services by Corvids as restoration method, I submitted a paper on the role of acorn size in determining early growth parameters in island scrub oaks. The proceedings, published as a General Technical Report, contain more than 20 papers on various aspects of oak biology, sociology, and economics. An interesting read for anybody who likes oaks and their role in ecosystems and society.
For the 19th time, Walt Koenig has put together his acorn report. Check it out below!
In order to expand our understanding of seed production in oaks on the California Channel Islands, we recently began annual acorn surveys on Santa Rosa Island (SRI), the second largest island off the California coast. The island, which has recently been opened for public access, is home to the CSU Channel Islands Field Station managed by Dr. Cause Hanna. Similar to Santa Cruz Island (SCI), SRI harbors island oaks (Quercus tomentella), island scrub oaks (Quercus pacifica) and coast live oaks (Quercus agrifolia). Scott Sillett, a research ecologist at the Smithsonian Conservation Biology Institute's Migratory Bird Center, and I became interested in the spatial and temporal variation of seed production on the Channel Islands because of the crucial role that oaks play in the recovery of the islands from human impact. Acorns also provide subsistence to a number of bird species, including acorn woodpeckers (Melanerpes formicivorus) and island scrub-jays (Aphelocoma insularis) which are endemic to SCI.
Quantifying the patterns of acorn production in oaks will thus allow us to test hypotheses about the drivers underlying the variation, as well as tie the availability of seeds to demographic parameters of acorn-dependent species. To get an estimate of the yearly acorn production, we mark individual trees and conduct timed acorn counts, providing a measure of relative acorn crop. A single year of data will tell us how much variation there may be among trees, but the true value lies in the repeated visits of these trees over the years. With a sufficient number of years in the data set, we can determine whether oaks on the Channel Islands behave similar to mainland trees, and whether they show synchronized seed production patterns, also called mast-seeding behavior. We can also investigate what role of abiotic parameters (temperatures, precipitation, wind etc) have in shaping annual seed production. Since oaks play a central role in the terrestrial ecosystem of the islands, insights derived from these studies will be of value to scientists and conservation practitioners alike.
To reach Santa Rosa, we boarded a three-hour boat ride in Ventura, CA, that took us along the south side of Santa Cruz Island and dropped us at the new pier in Becher's bay on the northeastern shore. The half-mile trek to the field station quickly reminded us that we were far away from the busy Southern California infrastructure, but also that we packed too much gear. Once settled in, we were introduced to Jay Woolsey, a highly motivated CSUCI undergraduate who started working on island oak populations on SRI. Over the next two days, we estimated the acorn crop of more than 70 trees and found a surprisingly large number of acorns. Many of the oaks, however, still had piles of last year's acorns below them, dried out and dead, reminding us that many functions of the ecosystem have not returned to a natural state. During a break from our counts, Dr. Hanna also provided us the opportunity to inspect habitat restoration efforts, as well as a large beach full of California sea lions (Zalophus californianus) and elephant seals (Mirounga angustirostris). SRI is an important hauling and breeding site for a large number of pinnipeds, as well as seabirds. Finally, as it was time to leave the island after many hours of hiking and data collection, the skies opened up and rain started to pour. In light of the four-year drought, our hearts rejoiced, but after a good hour of loading gear and waiting at the pier, we were all glad to find a dry spot on the boat back to Ventura.
The 2015 acorn season is in full swing. Here at Hastings Natural History Reserve, the valley oaks, blue oaks and canyon live oaks are carrying acorns that are soon ripe. There are also a few acorns on coast live oaks and California black oaks, but only on very few trees. This field season, I am lucky to have two talented young biologists assist me with field work. Jenna Kohles, who graduated from Clemson and plans on doing graduate work with bats, and John Zeiger, a Cornell graduate with bird fever, have joined me in the beginning of September to collect data on acorn crops and their fate.
Acorn-fiend-in-chief Walt Koenig and his partner in crime Jean Knops made a quick stop at Hastings last week before they set out for the annual California Acorn Survey (check out the project summary here). At the end of the their tour de force throughout California's most beautiful oak habitat (and taco shops), they will be joined by Ian Pearse, another Quercophile, and we will melt minds for the next papers that we will write together.
Later this fall, I will join forces with Scott Sillett from the Smithsonian Institution, and conduct our own annual acorn surveys on Santa Rosa and Santa Cruz, the two largest islands in the Channel Island National Park. While our data set is dwarfed by the Walt & Jean's data, this is already the 8th year that we count acorns on island scrub-oaks and coast live oaks. Such long-term data is extremely valuable, and will hopefully allow us to learn much more about the drivers and consequences of seed production in oaks, and how that affects jays, woodpeckers, and all the other critters that love acorns.
May the force of the acorn be with you!
After a long wait, our paper on the stand structure and acorn production of island scrub-oaks has finally been published. Find it, along with many other interesting contributions, in the Monographs of the Western North American Naturalist [link]
Ian Pearse, my predecessor as Walt Koenig's postdoc at Hastings, just spearheaded the publication of our newest paper in Ecology. Initiated by my good friend Kyle Funk, this work on pollen availability, and its interaction with flower production and abortion in the valley oak (Quercus lobata) provides an important contribution towards the lively scientific discussion about the drivers of masting behavior in wind-pollinated species. Using a clever mix of pollen addition experiments, flower counts and acorn counts, the paper shows that in years that are suitable for acorn production, pollen addition can increase acorn crop significantly, thus suggesting that these oaks are indeed pollen-limited to some degree!
After plowing through a pile of applications by an impressive group of young biologists, I am pleased to present the newest crew members for the western scrub-jay / oak project. Kachina Rowland is from Oregon and attended Humboldt State. Spencer Schubert is from Illinois and attended St. Olaf's College in Minnesota. The two stood out with great experience and background, and especially the desire to conduct their own small research project. Starting in late August, we will make an effort at figuring out another piece of the jay-oak interaction puzzle. Exciting stuff!
Almost, our ambassador woodpecker, is ready to hang out with new friends...