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Wisconsin Big Days -Why and How

A personal perspective

by Randy Hoffman

Since 1976, I participated in more than forty Big Day counts throughout most of the state.  These Big Days are attempts to see and hear as many bird species as possible within one calendar day. They oft times involve putting several hundred miles on a car and making abbreviated stops to check off species on the state's list.

Personally, I view these Big Days not so much as a competition against others, but a competition with myself to understand bird/habitat relationships and the intricacies of migration.  Another stimulating value to me is the perceived need to mold the multiple facets of a Big Day into a formulated plan.  Often winter or early spring strategy sessions help develop a new or alternative routes.  Furthermore, pre-count scouting will change earlier strategies and require changes.  Finally, to complicate things more, events on the Big Day require additional changes in plans due to local conditions. Beyond the bird knowledge aspect, Big Days are also a vehicle to concentrate my love of birding into a focused time frame.

Big Days are designed to count as many bird species as possible within a 24-hours of one calendar day. They were developed to foster friendly competition amongst birders.  Occasionally, friendly competitions went beyond their intended goals and guidelines had to be developed.  Limits are placed on counts to assure some consistency, for example leghorn chickens and emus are not eligible to be added.   Different  "rules" are applied by various birding organizations such as WSO or the American Birding Association.  These rules provide a basis for standardization so the count of any group can be compared to another.

When I first began serious birding in the mid-1970s, I spent almost all of my spare time in the pursuit of birds.  Everything about birds was new and exciting.  Birds challenged me around every corner.  I sought others with a similar passion for birds.  Through mutual interests, I was asked to participate in the Dane County May Day count.  This exercise introduced me to the world of 24-hour observation and the world of nighttime birding.

As the years progressed, the total time spent birding throughout the year waned as my family responsibilities grew.  However, I still continued to conduct one or more Big Day counts annually.  To me these counts provided an opportunity to pursue the attainment of migration knowledge and habitat utilization that drives my interest, while at the same time birding during the year became less and less.

Over the years, these Big Days had various results.  Some were successful, while others bombed miserably.  Each year added a new twist.  What was the best time?  Could more species be added if we were flexible and picked the right day?  Should we scout more?  These were some of the question asked each year.

For many years, my primary Big Day partners (Al Shea, Mark Peterson, and Daryl Tessen) and I developed numerous routes and schemes to count as many species as possible.  Most years our counts ranged from 170 to 183 species, but a few counts barely reached 150.  I ran a few counts by myself in northwest Wisconsin, where twice totals reached into the 190s.  Albeit, these single person counts do not hold as much esteem, because there is not a second person verification.  The two or more person record count of 185 was set by Jeff Baughman, Tom Schultz, Wendy Schultz, and Bill Stott in 1990.

Big Day birding seemed to come to a penultimate position in 1997, when my long-time big day compatriot, Al Shea and I recorded 208 species in a less than 21 hours.  Why did this big day succeed in shattering the previous two or more person record count of 185 and the one person record of 197 by so much?  Was it the migration, the weather or the route?  Why had routes run for many years by others with better identification skills failed to eclipse the 200 barrier?  These questions occupied my mind off and on throughout the next two years, until I decided to analyze my past big days.


My conclusion is all big days are not equal and they cannot be compared by total numbers alone.  Different parts of the state do not have the same pool of species available and if compared must be compared against the regional pool available and not statewide.

My reason for this statement is the complexity of species habitats across an area as diverse as the entire state.  In addition, there are numerous nuances of migration that are not equally applicable in different parts of the state or even within different assemblages of species.  I analyzed my forty-six big day efforts from five geographic areas of the state: east central (EC), southern (S), central (C), northwest (NW), and northeast (NE).  I reviewed the species recorded from the Big Days and determined four categories of species constitute the pool of potential countable birds.

1.  Resident and early migrants that are on territory
2.  Recent migrants that nest in the area and may not be dependent on a "good" migration day.
3.  Northern shorebirds that depend on timing and habitat more so than a preferred migration day
4.  Migrants that do not nest in the area.

Category 1:

Within this category, the pool of potential species varies by region.  The first group in this category is species that are so ubiquitous, such as American crow, American robin, or killdeer; they can be virtually guaranteed every year regardless of where a birder is in the state.  These are noted with an X in Table 1 as easy .  This first notation can also apply to birds regionally, but regions are different when it comes to high probability of recording species. A second X notes those species that utilize many habitats and can be almost certain if enough time is spent birding in a region. These X is noted under the appropriate geographic area.

The second notation is H representing a high probability that the species should be counted on if the appropriate habitat is visited under good viewing and listening conditions and a preferable time of day (morning for passerines), and again noted under the appropriate region.  A final notation encompasses birds that are more problematic with limited habitat or populations within the big day region.  These are listed as scouting required (S) to locate sites in each geographic area.  This group of birds cannot be entire counted even if the conditions are right and less so if observational conditions are marginal.  My evaluations of past counts indicate on any Big Day between 60 and 95 % of the birds listed as S can be found in the south and 50 to 80 % can be found in the north.

Category 2:

The second category is found in Table 2.  This group is those species migrating later, whose detectability may be dependent as much on time of the count as the route.  Some of these birds are common, and if the Big Day is run before they return, they will probably be missed.  Table 2 lists these later migrant species with similar analyses and notations applied as in Table 1.  An additional category of (M) for migrant is added with progressively fewer pure migrants as you move north.  These migratory birds have shown a similar pattern to the scouting birds for easy of finding during a count.  My data again found 60 to 95% of the migrants were recorded in the south and 50 to 80% were recorded in the north.

Category 3:

This group includes shorebirds and American pipit, which can be exceptionally abundant or nonexistent depending on habitat availability.  The key factors are habitat and time of the month.  Table 3 indicates the shorebirds regularly encountered on big days and the time of the month they are most easily observed.   This group is sometimes almost entirely missed or they can be numerous.  Anywhere from one to twenty-two species is possible.

Category 4:

The final category contains rare birds.  These birds listed in Figure 1 are those found more than once on big days.  They are comprised of late migrants, uncommon species or wanderers.  An average of past counts indicates between one and six species are encountered on any big day count.

SPECIES Easy EC South Central NW NE
Common Loon - S - H H H
Pied-billed Grebe - X H X X X
Red-necked Grebe - S S S S -
Double-crested Cormorant - X H X X X
American Bittern - X H X X X
Great Blue Heron X - - - - -
Great Egret - X X X S S
Green Heron - H H H S S
Black-crowned NightHeron - X X X S X
Trumpeter Swan - - - S S -
Mute Swan - S S S S S
Canada Goose X - - - - -
Wood Duck X - - - - -
Green-winged Teal - S S S S S
Black Duck - S S S S H
Mallard X - - - - -
Northern Pintail - S S S S S
Blue-winged Teal X - - - - -
Northern Shoveler - H H H S S
Gadwall - H H H S S
American Widgeon - S S S S S
Redhead - X X X S S
Ring-necked Duck - - S X X X
Lesser Scaup - H S S H S
Greater Scaup - H - - S -
Hooded Merganser - S S H H S
Red-breasted Merganser - X S S H H
Ruddy Duck - X X X S -
Turkey Vulture - X X X X S
Osprey - - - S H H
Bald Eagle - S S S H H
Northern Harrier - S S H H S
Sharp-shined Hawk - - - S S S
Cooper's Hawk - S S S S -
Red-shouldered Hawk - S H H S S
Broad-winged Hawk - - - H H H
Red-tailed Hawk X - - - - -
American Kestrel X - - - - -
Gray Partridge - S S S - -
Ring-necked Pheasant - H H H S -
Ruffed Grouse - S S H H H
Prairie-Chicken - - - H - -
Sharp-tailed Grouse - - - H H S
Wild Turkey - H H H S S
Bobwhite - S S S - -
Virginia Rail - H H H H H
Sora - H H H H H
Common Moorhen - S S S - -
American Coot - H H H S -
Sandhill Crane - H S X X H
Killdeer X - - - - -
Spotted Sandpiper - H H H X X
Common Snipe - S S X X H
American Woodcock - H H H H H
Bonaparte's Gull - H - - H -
Ring-billed Gull - X S H X X
Herring Gull - X S H X X
Caspian Tern - H - S X H
Common Tern - X S H X X
Forster's Tern - X H X X X
Black Tern - X X X X H
Rock Dove X - - - - -
Mourning Dove X - - - - -
Screech Owl - S H H - -
Great-horned Owl - H H H H H
Barred Owl - H H H H H
Long-eared Owl - - - S S S
Short-eared Owl - - - H H -
Saw-whet Owl - - - S H H
Chimney Swift X - - - - -
Belted Kingfisher - H H H H H
Red-headed Woodpecker - H H H H S
Red-bellied Woodpecker - H H H H S
Yellow-bellied Sapsucker - S S H H H
Downy Woodpecker X - - - - -
Hairy Woodpecker - H H H H H
Black-backed Woodpecker - - - - S S
Common Flicker - H H H H H
Pileated Woodpecker - S S H H H
Eastern Phoebe - H H H H H
Horned Lark - H H H S S
Purple Martin - X H H H H
Tree Swallow X - - - - -
Rough-winged Swallow - H X X H H
Bank Swallow - H H H H H
Cliff Swallow - H H X X X
Barn Swallow X - - - - -
Gray Jay - - - - S S
Blue Jay X - - - - -
American Crow X - - - - -
Northern Raven - - - H X X
Black-capped Chickadee X - - - - -
Boreal Chickadee - - - - S S
Tufted Titmouse - - H S - -
Red-breasted Nuthatch - S S H H H
White-breasted Nuthatch X - - - - -
Brown Creeper - S S H H H
House Wren X - - - - -
Winter Wren - - S S H H
Sedge Wren - H H X X H
Marsh Wren - H H H H S
Golden-crowned Kinglet - - - S H H
Ruby-crowned Kinglet - - - S S S
Blue-gray Gnatcatcher - X X X X S
Eastern Bluebird X - - - - -
Hermit Thrush - - - H X X
American Robin X - - - - -
European Starling X - - - - -
Northern Cardinal - X X X X H
Eastern Towhee - H H H H H
Chipping Sparrow X - - - - -
Field Sparrow - H X X H S
Vesper Sparrow - X X X H H
Lark Sparrow - - S S S -
Savannah Sparrow X - - - - -
Grasshopper Sparrow - H H X S S
Song Sparrow X - - - - -
Swamp Sparrow X - - - - -
Dark-eyed Junco - - - S S S
Lapland Longspur - S S S - -
Red-winged Blackbird X - - - - -
Eastern Meadowlark - X X X X H
Western Meadowlark - S H H H S
Yellow-headed Blackbird - X X X X S
Brewer's Blackbird - S S H X H
Common Grackle X - - - - -
Brown-headed Cowbird X - - - - -
Purple Finch - S S H H H
House Finch X - - - - -
Red Crossbill - S S S S S
White-winged Crossbill - S S S S S
Pine Siskin - S S S H H
American Goldfinch X - - - - -
Evening Grosbeak - - - S X X
House Sparrow  X - - - - -

Least Bittern May 10 - 15 H H H S S
Yellow Rail May 10 - 15 S - S S -
King Rail May 1- 5 H H H S -
Upland Sandpiper April 25 - May 1 S S H S S
Common Nighthawk May 15 - 20 X X X X X
Whip-poor-will May 5 -10 H H X X X
Black-billed Cuckoo May 15 - 20 H H X X X
Yellow-billed Cuckoo May 20 - 30 H H H S S
Ruby-throated Hummingbird May 10 - 15 H H X X X
Olive-sided Flycatcher May 15 - 25 M M M H H
Eastern Wood-Pewee May 10 - 15 X X X X X
Yellow-bellied Flycatcher May 15 - 25 M M M H H
Acadian Flycatcher May 15 - 20 S H H - -
Alder Flycatcher May 15 - 20 H H X X X
Willow Flycatcher May 15 - 20 H H H S S
Least Flycatcher May 5 -10 X X X X X
Great Creasted Flycatcher May 1 - 5 X X X X X
Eastern Kingbird May 1 - 5 X X X X X
Veery May 10 - 15 H H H H H
Gray-cheeked Thrush May 10 - 25 M M M M M
Swainson's Thrush May 10 - 25 M M M S S
Wood Thrush May 10 - 15 X X X H S
Gray Catbird May 1 - 5 X X X X X
Brown Thrasher May 1 - 5 X X X H H
Cedar Waxwing May 10 - 30 H H H X X
Bell's Vireo May 15 - 20 S S S S -
Blue-headed Vireo May 1 - 15 M M S H H
Yellow-throated Vireo May 5 -10 X X X H H
Warbling Vireo May 1 - 5 X X X H H
Philadelphia Vireo May 10 - 25 M M M M M
Red-eyed Vireo May 10 - 15 X X X X X
Blue-winged Warbler May 5 -10 H H H S -
Golden-winged Warbler May 5- 15 M M X X H
Tennessee Warbler May 15 - 25 M M M M M
Orange-crowned Warbler April 25 - May 10 M M M M M
Nashville Warbler May 1 - 15 M M X X X
Northern Parula  May 1 - 15 M M M H H
Yellow Warbler May 5 -10 X X X X X
Chestnut-sided Warbler May 1 - 15 M M H X X
Magnolia Warbler May 5 - 20 M M M S S
Cape May Warbler May 5 - 20 M M M S S
Black-throated Blue Warbler May 10 - 20 M M M S X
Yellow-rumped Warbler April 25 - May 15 M M H X X
Black-throated Green Warbler May 5 - 15 M M S X X
Blackburnian Warbler May 5 - 15 M M M H H
Pine Warbler April 25 - May 10 M M H H H
Palm Warbler May 1 - 15 M M M M M
Bay-breasted Warbler May 10 - 25 M M M M M
Blackpoll Warbler May 15 - 30 M M M M M
Cerulean Warbler May 5 - 15 H H H S -
Black & White Warbler May 1 - 15 M M H H H
American Redstart May 10 - 15 X X X X X
Prothonotary Warbler May 5 - 10 S H H S -
Ovenbird May 1 - 5 X X X X X
Northern Waterthrush May 1 - 15 M M S H H
Louisiana Waterthrush April 25 - May 1 S H H S -
Kentucky Warbler May 10 - 15 S H S S -
Connecticut Warbler May 15 - 30 M M S H S
Mourning Warbler May 15 - 30 S M S H H
Common Yellowthroat May 1 - 5 X X X X X
Hooded Warbler May 10 - 15 H S S S -
Wilson's Warbler May 10 - 25 M M M M M
Canada Warbler May 15 - 25 M M H H H
Scarlet Tanager May 5 - 10 X X X X X
Rose-breasted Grosbeak May 5 - 10 X X X X X
Indigo Bunting  May 10 - 15 X X X X X
Dickcissel May 15 - 30 S S S S -
Clay-colored Sparrow May 1 - 5 S S X X H
Henslow's Sparrow May 10 - 15 H H X S -
LeConte's Sparrow May 10 - 15 S - S H S
Nelson's Sharp-tailed Sparrow May 15 - 20 - - - S S
Lincoln's Sparrow May 10 - 20 M M M H H
White-throated Sparrow May 1 - 15 M M H X X
White-crowned Sparrow  May 5 - 25 M M M M M
Bobolink May 1 - 5 H H X X H
Orchard Oriole May 5 - 15 S H H H -
Baltimore Oriole May 1 - 10 X X X X X

SPECIES Ave. Migration Dates
Black-bellied Plover May 15 - 30
American Golden Plover May 1 - 30
Semipalmated Plover May 10 - 25
Greater Yellowlegs May 1 - 15
Lesser Yellowlegs May 1 - 20
Solitary Sandpiper May 1 - 20
Whimbrel May 15 - 25
Hudsonian Godwit May 10 - 25
Marbled Godwit May 10 - 20
Ruddy Turnstone May 20 - 30
Red Knot May 20 - 30
Sanderling May 10 - 30
Semipalmated Sandpiper May 5 - 30
Western Sandpiper May 15 - 30
Least Sandpiper May 5 - 30
White-rumped Sandpiper May 15 - 30
Baird's Sandpiper May 15 - 30
Pectoral Sandpiper May 1 - 20
Dunlin May 10 - 30
Stilt Sandpiper May 10 - 15
Short-billed Dowitcher May 10 - 25
Long-billed Dowitcher May 5 - 20
Wilson's Phalarope May 10 - 25
Red-necked Phalarope May 20 - 30
American Pipit May 10 - 25


Regularly Occurring Rare Species

Horned Grebe
Eared Grebe
American White Pelican
Snowy Egret
Cattle Egret
Yellow-crowned Night-Heron
Tundra Swan
Surf Scoter
Common Merganser
Northern Goshawk
Rough-legged Hawk
Peregrine Falcon
Spruce Grouse
American Avocet
Franklin's Gull
Glaucous Gull
Great Black-backed Gull
Carolina Wren
Northern Mockingbird
Loggerhead Shrike
White-eyed Vireo
Yellow-throated Warbler
Prairie Warbler
Worm-eating Warbler
Yellow-breasted Chat
Summer Tanager
Harris Sparrow

Table 4 is the compilation of all the possible species in the different geographical areas.  This table assumes the observes will have good observational conditions for most of one calendar day.  The ubiquitous birds are the total of the easy list and the X's in Tables 1 and 2 for each geographical area.  The highly probable species should be listed by visiting the right habitat category.  This grouping adds the H's from Tables 1 and 2.  The scouting required - maximum assumes 95% of the birds will be found in the south and 80% in the north.  The minimum category assumes 60% in the south and 50% in the north.  The migrant passerines maximum and minimum assumes the same percentages as scouting.  The shorebird and rare bird categories assume maximums and minimums as described in the text.

This analysis indicates the area of the state with the highest potential for big numbers is the central part of the state.  I believe this is due to a larger diversity of territorial species than elsewhere.  The counts to the south and east depend more on migrations and reduced habitat diversity which exerts more volatility into a big day than central Wisconsin.  The north has even more resident bird stability than central Wisconsin, but the total species pool available and shorebird habitat limits the total numbers.  Of course weather plays a major role in any count, and poor weather can reduce minimum count totals below expectations.

Ubiquitous species 71 64 82 84 72
Should get by visiting the right habitat 47 51 63 58 55
Scouting required - maximum 40 37 39 40 36
Migrant passerines maximum 28 28 17 8 8
Shorebirds average maximum 22 22 22 19 16
Rare birds average maximum 6 6 6 6 6
- - - - - -
Total maximum 214 208 229 215 191
- - - - - -
Ubiquitous species 71 64 83 84 72
Should get by visiting the right habitat 47 51 63 58 55
Scouting required ave. minimum 25 23 25 26 22
Migrant passerines ave. minimum 15 15 9 4 4
Shorebirds minimum 1 1 1 1 1
Rare birds ave minimum 1 1 1 1 1
- - - - - -
Total minimum 160 155 181 174 155

Types of Big Days

The above analysis was compiled for planning and comparative purposes.  These intensively planned and coordinated Big Days are not the only ways to conduct a Big Day.  I believe Big Days can be separated into at least six different types and there may be more.  Each type has its own rewards and each had its own approaches to success.

1.  A Big Count - this Big Day tries to get the largest number possible for total species.

2.  A Big Migration Day - this count tries also to get the largest number possible, but the limitation of a smaller pool of territorial species and the volatility of migration requires different strategies. 3.  A Big Migration Day - Rare Birds - This emphasis is similar to the big migration day, but special emphasis is placed on scouting and visiting rare species locations.  This type of big day is often used by persons keeping year lists as a way to fill out their lists in a different part of the state.  Methods are the same as #2 with the additional of scouting for and chasing rare species.

4.  Migration HotSpots - this Big Day focuses on migrants by planing a route that visits known concentration areas for migrants.  The methods are similar to #2 without the scouting and visiting habitats for uncommon species.

5.  Exploratory Big Days - these can be either designed like #1 or #2, but they visit areas unknown to the observers.  These counts are for those who have a sense of discovery and a passion for the unknown.

6.  One Site - These big days are limited to a very small geographic area.  By visiting one site year after year, the observers can get a comparative sense of annual migrations from the same spot.

All six types have their intrinsic values, and likewise with the regional differences, they are not conducive to comparison of total numbers between types.  Although Al Shea and I recorded 208 total species in one day, I do not consider that my best big day.  We saw 90.8% of the potential species for the route.  Similarly, the same year, Schlutz, Baughman, Tessen, and Wood had 191 species that represented 89.2% of their potential.  Running nearly the same routes in 1998, Al and I had 193 total species representing  84.2% of the potential, and the other group had 182 total species representing 85% of the potential.  The 182 species total was a better big day than 193.  My second best big day tallied 197 species in northwest Wisconsin which comprised 92.9% of the potential.  My best big day was done entirely within the boundaries of Wyalusing State Park where I tallied 122 species which comprised 93.8% of the potential.  It also had zero miles by car and 9 miles on foot.

10 Keys to a successful big day.