On 14 April 2013, my wife Marta and I unexpectedly had a mammal “big day” in California. We left our home in Angwin (Napa Valley) at 3:30 am to drop off a visiting friend, Bixis Colina, at the airport in Sacramento. A few hundred meters from home a GRAY FOX trotted across the road. Within the next half hour a VIRGINIA OPOSSUM waddled along the road, a BLACK-TAILED JACKRABBIT hopped onto the road and a RACCOON hustled across the road as we sped through Pope Valley and Chiles Valley. Later, when a BOBCAT (my lucky 13th!) dashed across the highway near Lake Berryessa, I realized we were going to have a mammal big day! I’d had many bird big days (up to 198 species in Washington state), but never a mammal big day. Soon we saw a few MULE DEER beside the highway.
While returning from the airport after sunrise, I stopped at several places along Putah Creek to search for River Otters, where I had seen them before. Unfortunately I didn’t have any luck with the otters, but I enjoyed rock climbing on some huge boulders while Marta implored me not to fall. And then I spotted a tiny black-and-white dot moving on a distant hill across the river, whipped out the big camera, and photographed a STRIPED SKUNK! We also saw a few WESTERN GRAY SQUIRRELS in the trees and when we visited a picnic area at Lake Berryessa we found a CALIFORNIA GROUND SQUIRREL.
A distant Striped Skunk photographed through a 400 mm lens.
We were both recovering from colds and had planned to relax at home after returning from the airport, but after taking a long nap (we were really sleepy!) and eating lunch, we decided to have a romantic date on the coast. At Bodega Bay we saw several CALIFORNIA SEA LIONS. It was super windy so Marta didn’t join me when I hiked out to a point to search for other pinnipeds on a tiny offshore rock. With my binoculars I tried to pick out a Steller’s Sea Lion among the California Sea Lions on the distant rock, and took some photos with a 400 mm lens; I think I can make out at least one in my photos, but I’m not certain so I’m not counting it. Then we sped to Goat Rock State Beach, where we saw a few dozen HARBOR SEALS, including an adorable white pup.
At several wetlands along the coast I searched for River Otter, including a pond where I had seen them once previously, but failed to find any. Disappointed but not surprised, we drove home. Alas, I had to pee, so I stopped beside the road high above the Russian River. A moment before returning to the car, I magically spotted through the Redwood trees a lone RIVER OTTER swimming downstream! I dashed back to the car and managed to show it to Marta, who thought I was joking. It was my best pee stop ever! Just before dark we arrived at the campus of Pacific Union College, where we live and work, and spotted several WESTERN PIPISTRELLES (tiny bats) fluttering above the sewage ponds.
Our final tally was a lucky 13 species on Saturday the 13th (luckily not Friday!), including my 13th Bobcat. All were free-ranging native species found within Napa, Yolo and Solano Counties of northern California.
To put our big day into perspective, I did an online search for previous mammal big days but found very few reports. The world record appears to be 42 species, seen on 29 May 2004 in Tanzania by Charles Foley (see “A Mammal Big Day,” published in Birding 37:128-130, 2005).
In North America, the highest one-day tally I could find was 17 species, reported from Marin County, California, by the late Rich Stallcup, but no date or list of species was provided (www.prbo.org/obs_cms/index.php?module=browse&browse_issue_num=154&browse_article_num=212&chooseIssue=1).
In late September 2011, Brian and Eileen Keelan saw 14 species, including three during a whale-watching trip, in Monterey County, central California; an additional two species were captured in traps (public.keelan.warpmail.net/chr11.pdf), but as Charles Foley reasoned in his article cited above, only free-ranging native species should be counted due to restrictions in some parts of the world on trapping.
After I posted a short summary of our big day on a birding listserve for the northern San Francisco Bay area, a few others replied that they had seen more species of mammals in a day. Peter Pyle reported doing informal mammal big days when returning from the Farallon Islands, and once tallied 17 species (18 if the introduced House Mouse is included), which ties Rich Stallcup’s record, but he could not remember the day or year, which occurred during the late 1990s or early 2000s. Alan Wight reported that his Point Reyes Bird Observatory Birdathon team, the Sonoma Gray Jays, had been keeping track of their mammal sightings while searching for birds since 2005, and had recorded up to 16 species (17 if the introduced Wild Boar is included) on 25 September 2010.
Considering the tremendous efforts of birders to establish big day records throughout North America, which have been compiled for decades by the American Birding Association, surprisingly little effort has been made to establish a mammal big day record. Based on the information that I have found, the North American mammal big day record for native species appears to be a modest 17 species, set independently by Richard Stallcup and Peter Pyle. However, it is quite possible that somebody else has observed more. A more serious effort combining marine and terrestrial mammals in California could potentially push the list much higher. It is high time for somebody to up the ante!
Floyd E. Hayes
Department of Biology
Pacific Union College
Angwin, California, USA