The new Atlas is big, really big. It rivals many textbooks in size simply because of the vast amounts of data it has managed to pack in for each species. The cover of the new Atlas of Breeding Birds is again fantastic, painted by Julie Zickefoose and playing along the theme of the cover she painted for the first Atlas, this time featuring a male Brewster’s Warbler (F1 cross between Blue-winged and Golden-winged Warblers) carrying food to its mate, a Golden-winged Warbler.
The new Atlas of Breeding Birds is a veritable treasure trove of information. The people working on and for the atlas collected a monumental amount of data, and all of that is in the atlas in some form or another, from landcover types, extent of deer browse and hemlock wooly adelgid, to number of bird houses and natural cavities in the surrounding area. Over 1.5 million bird sightings were recorded during the 5 year effort, creating a snapshot of Pennsylvania’s breeding birds in great detail.
The extensive statewide point counts (that I helped with) coupled with some population modeling means that we can get a decent idea of how many pairs of breeding birds there are for the 115 most numerous species. Any guesses on the Top 5 most common species breeding in PA? Song Sparrow comes in at 2.99 million pairs, Chipping Sparrow at 2.98 million pairs, Red-eyed Vireo at 2.83 million pairs, American Robin at 2.45 million pairs, and Gray Catbird at 2.45 million pairs. If you ever wondered why you always got so tired of catbirds soon after they appeared in the spring, now you know, it’s because there are so many of them! The most common warbler is the Ovenbird and clocks in at respectable 2.38 million pairs. Other fascinating analyses pinpointed the species that showed northward and southward range expansions and retractions, trends that may have taken much longer to detect without the Atlas.
A typical species account features an overview of the bird in Pennsylvania, and a portrait on the left page (Figure 4). The overviews were all written by people very knowledgeable of that species, as well as its conservation status in Pennsylvania. There are many great facts to be gleaned from the text, such as the Red Crossbill types that have been recorded in Pennsylvania (1, 2, 3 and 10). On the right side of the two-page spread are the range and occurence maps (Figure 5). The top large map shows the highest breeding evidence reported in each block. Below is a map that shows changes in distribution from the last atlas, with blocks colored yellow if there was breeding behavior detected in the first atlas, records from the second atlas in blue, and blocks with detections in both atlases colored green (yellow + blue = green).
The most common species also have an abundance map, created from data I and ~12 other field ornithologists collected over five field seasons (Figure 5). From our point counts that covered the state at the density of roughly 1 point per every square mile, the authors were able to create maps showing the density of breeding species across the state at a much finer detail than has ever been created before. Compare the abundance map created from June-July eBird data (Figure 6a) and the corresponding abundance map from the atlas (Figure 6b). The level of detail in the atlas maps is phenomenal and you can quickly pick out, if you know PA geography, that Black-throated Blue Warblers are breeding at higher elevations.
Black-throated Blue Warbler is a fun species to look at because, as you can see in the BBS trend on the map page, they have been increasing in Pennsylvania since at least the 1960’s. The Pennsylvania forests have been maturing, and increased deer harvest may have allowed shrubby understory vegetation to recover, providing more suitable breeding habitat for this species that thrives in areas with a thick rhododendron and mountain laurel understory. It is exciting to realize that the forests in PA are providing more and more habitat for many of our breeding species as they mature.
This year has been an especially strong year for finches in the state, so I thought it would be interesting to look at some of the graphics included in the Second Atlas for several of the finch species that breed in the state. House Finches (Figure 7) are common across the state as breeders, and were recorded almost everywhere in the state except in the north-central counties which are dominated by core forest, not ideal habitat for House Finches. Purple Finches (Figure 8) are restricted to breeding in more northern and higher elevation parts of the state and this is obvious in the map of breeding evidence. Generally they are also absent from the Ridge-and-Valley region until you get up to the Poconos. Red Crossbills (Figure 9) are one of our rarest breeders and are found in high elevations of the Allegheny Plateau and the Appalachian Mountains. They were primarily detected in rarely visited high-elevation bogs in northern Pennsylvania.
The newest edition of the Atlas of Breeding Birds in Pennsylvania sets the standard for new breeding bird atlases going forward. The planning, analysis, and every pertinent detail is meticulously recorded so that future atlases anywhere have a wealth of information to start with. If you have any interest in bird distributions, range changes, breeding birds, or birding in Pennsylvania, this book will be indispensable. I realize that I am biased due to working on the project for several years, but I encourage you to add it to your collection and see for yourself.
Many thanks to Danny Bellet and The Pennsylvania State University Press for providing a copy of the atlas and images for this review.