Friday, May 4, 2018

4 May 2018: Recap and Green Big Day planning

Rest days are important! They mean that I will be able to keep biking and birding intensively. We got a lot of rain overnight, pretty much from dusk til dawn, so there probably wasn't a lot of bird movement. So it was a good day for a rest day.

I took the opportunity to crunch some numbers. Here's what 2018 has looked like so far:
The last week has brought a real change in the rates of accumulation of species, miles (includes biking to/from birding areas as well as travel while birding), and birding hours, though the change in the last is hard to see on this scale.

Then I thought I'd see how this year compares to last year, when I was also bike-birding enthusiastically. I didn't track my miles or hours then, but all my checklists are in eBird, so it's easy to pull my two year lists and compare the number of species accumulated by each day of the year:

In 2017, I was birding less intensively early in the year than I did this year. Lake Onalaska (our local chunk of the Mississippi River) started thawing earlier, and once it thawed, the weather stayed warm. In contrast, this year the thaw stalled for a while and then we had a few periods of late snow. Last spring, north winds were very frustrating early in the period of what should have been peak migration, and the species only trickled in until the winds switched. This year we've had a good mix of winds, but it stayed cold later, meaning the insectivores were in no rush to get here. When the winds switched to the south early this week, temperatures soared (high of 60 one day to high of 80 the next!) and the species flooded in, with normally early and late migrants arriving together. I added 41 species to my year list from Monday through Thursday of this week!

Once we consider the vagaries of the weather, it seems like my list for this year is fairly well on par with my list around the same time last year. That's a little disappointing, because I wanted this year to be bigger! But last year I was also actively birding during spring migration, and accumulated a very good list for the county. This year, the main difference will show when I take longer trips to different parts of the state (health and weather allowing - my intended early spring trip was already scrapped when it kept snowing!). In 2017, my year list plateaued at 199 at the end of spring migration and stayed there until the fall, when I picked up a few more species and ended with 213. This year, I hope to keep growing the list, at least in fits and starts, through the summer and fall with multi-day adventures. I've also had several good species that I never found last year, including Hoary Redpoll, Iceland Gull, Lesser Black-backed Gull, and Red-necked Grebe, so that bodes well for the year-end total - though I might well miss a couple that I found last year.

Each year, I like to do a Green Big Day during the peak of bird diversity in spring, when many local breeders have arrived but northern migrants are still moving through. Last year, I did mine on May 12th in La Crosse County. I ended the day with 110 species, 39 miles biked, and 5 miles walked. My strategy was to maximize diversity per mile - Big Days typically involve trying to reach as many different habitats as possible, but there were only so many habitats I could reach in one day on a bike in my home county. I was pleased with my total, which beat my previous Green Big Day in Manhattan, Kansas by one whole species!

This year, I've joined the Great Wisconsin Birdathon to help raise donations for the Wisconsin Bird Protection Fund with my Green Big Day, in addition to a year-end donation that I've pledged to make based on what I see this year. The Bird Protection Fund benefits a number of high-priority projects that are selected each year based on their conservation value. Donations to the fund go directly to protecting key species, including endangered Whooping Cranes and Kirtland's Warblers, and funding important initiatives like Bird City Wisconsin and the Wisconsin Breeding Bird Atlas. See the Bird Protection Fund website for details on those projects.

The Birdathon is like a walkathon, except you have a target number of species instead of a target distance or time to walk. Donations can be made as either a flat amount or a per-species amount. I'll be doing my Green Big Day in mid May in Trempealeau County. If you're interested and able to donate, I would be thrilled to have your support, and every dollar will go directly to the Bird Protection Fund.

For my Green Big Day this year, I'm planning big changes! A perusal of eBird data suggested that I can dramatically improve my species count by doing my big day in Trempealeau County, just to the north, instead of from home. Based on the frequencies of occurrence on eBird checklists (e.g. Species A is reported on 5% of checklists submitted during the second week of May), I might realistically be able to get 140 species - improving on last year by a whopping 30! I've set my Birdathon target a little lower, at 125, which I might be able to reach even if nothing goes as planned. I'm guessing that shorebirds will be the easiest group to miss, as habitat for them is sparse and dependent on receiving enough rain to flood some farm fields. 

The area I'll bird is 20-30 miles from home, and there's no way I'll have the energy to bike there and back AND do a Big Day all in one day. Luckily there's a very convenient campground in my target area, at Perrot State Park. I'll bike up the day before and camp overnight. The next day I'll be able to cover all of the major habitat types of this region over about 60 miles of biking. The State Park has excellent upland and bottomland forest; an agricultural area to the north offers various open habitats, some potentially flooded fields for shorebirds, and some stands of pine; and Trempealeau National Wildlife Refuge has marsh, open water, prairie, and shrubland, along with some younger stands of forest. I'll camp again that night, hopefully picking up some nocturnal species at the same time, and bike home the next day.

So, when's the Big Day? Timing is crucial. I used eBird data to see when diversity peaks in Trempealeau County:

In the above plot, the number of species recorded in eBird is shown for each week of the year. Each line shows the number of species recorded on some proportion of the checklists submitted that week. Weeks with <50 checklists are not considered because I wanted decent sample sizes, so 0 species are shown for those weeks.

My best guess is that species recorded on 5% of checklists would be potentially feasible to get during a Big Day. As it turned out, my total of 110 last year closely matched the number recorded on 5% of checklists in La Crosse for the second week of May. (The species list did not match exactly, but that's still a good ballpark for the number I might expect to find.) So if we look at the blue line (second from bottom), we can see that it peaks at 141 during the second week of May (I put a dotted line at the first week of May for reference), with the third week being a close runner-up (136 species). So I'm targeting May ~10-16th for my Big Day. I'll choose the exact day based on the weather forecast - the Big Day should be fairly calm and dry, and I'd prefer biking conditions to be reasonable the day before and after. Early in that period, south winds the night before would be helpful to bring in some new migrants.

Many Big Days involve intensive scouting, with birders going so far as to mark the territories of individual birds that they plan to use to check off a species. But here, I'll have many migrants on my list, and scouting would not be very helpful when turnover is so high. Regardless, I will likely not have a chance bird Trempealeau again before the Big Day - there's too much birding to be done! I don't want to sacrifice my year list for the sake of a Big Day list. But I've birded there several times in the past and have a very good idea of exactly where I want to go. I'll also have a chance to do a little scouting the previous afternoon/evening after I arrive, although I'll probably mostly use that for logistical purposes, such as scoping out where I can park my bike near the trail I plan to walk at dawn.

That's the plan - we'll see what happens! Stay tuned, and if you're keen to take this opportunity to donate to a good cause, you can help spur me on to dredge up as many species as I possibly can on my Green Big Day!

1 comment:

  1. Your trip sounds great! I can't wait to see what you come up with. My "big weekend" is May 18-20th, which I picked only because it worked best with my schedule. I would have loved to do it about 5 days earlier, but with work that was a no-go. My goal is to find species that will help me maximize my year list, but I will also be tracking each day's total to see what my biggest day will be. I think that May 18th will be it for me, since it is the earliest day but will also have me traveling through forest, grassland, and marsh. The other days won't have that diversity of habitats. Best of luck to you!