dantly that birds often have rather short lives; a five-year-old American robin is unusual, and a ten-year-old is almost unheard of. A few groups of birds, generally larger species that are effectively protected by habitat or law, such as many seabirds, swans, cranes, and some others, may have lifespans that approach those of humans. Yet, accidents, diseases, predators, starva- tion, and inclement weather all take their toll on wild bird populations, re- gardless of human efforts to help. In many regions of North America, the brown-headed cowbird, a “brood par- asite” that lays its eggs in other spe- cies’ nests and reduces the breeding success of its unwitting hosts, has had devastating effects on many na- tive songbirds, as it has expanded its range out of its native Great Plains (Johnsgard, 1997). Although adapted to prairie and forest edge habitats, forest fragmentation caused by lum- bering, road construction, and sim- ilar activities has placed many for- est-adapted species at risk to such parasitism.
Grassland-adapted species have declined greater nationally than have any other of the ecological categories recognized by the US Fish and Wild- life Service, with nearly 90% of the approximately thirty grassland spe- cies undergoing population declines. These long-term declining grass- land-dependent species include the Henslow’s sparrow, grasshopper spar- row, short-eared owl, greater prairie- chicken, field sparrow, eastern and
western meadowlarks, Brewer’s spar- row, chestnut-collared and McCown’s longspurs, and lark sparrow (Johns- gard, 2001b).
Of 220 species that probably or certainly currently breed in Nebraska, national Breeding Bird Surveys sug- gest that 90 of them have shown sur- vey-wide population increases be- tween 1966 and 2015, whereas 130 have exhibited probable population declines. It is notable that among Ne- braska’s mostly insectivorous passer- ines, more than twice as many species are declining than are increasing, sug- gesting that insecticides and other ag- ricultural biocides are taking a heavy toll on Nebraska’s bird populations.
Nebraska breeding species show- ing the highest rates of annual sur- vey-wide decline are the bank swal- low (5.33%), McCown’s longspur (4.19%), pinyon jay (3.69%), north- ern bobwhite (3.48%), mountain plo- ver (3.41%), pine siskin (3.67%), and Lewis’s woodpecker (3.42%). Al- though not currently known to be an in-state breeder, the greater sage- grouse also had a 3.41% annual rate of survey-wide decline. The five cur- rently most common breeding species in Nebraska are the mourning dove, brown-headed cowbird, eastern king- bird, red-winged blackbird, and barn swallow (Mollhoff, 2016); all appear to be declining.
Nebraska breeding species show- ing the highest rates of current annual survey-wide increase are the Eurasian collared-dove (27.18%), Canada goose (9.17%), wild turkey (7.5%), sandhill
M O N I T O R I N G N E B R A S K A B I R D P O P U L AT I O N S
crane (4.74%), glossy ibis (4.24%), hooded merganser (3.89%), and dou- ble-crested cormorant (3.76%). The surprisingly high rate of increase of the sandhill crane largely reflects range expansion and markedly in- creased numbers of the greater sand- hill cranes, especially its eastern population. Although not a current Nebraska breeder, the American white pelican also had a notable (4.82%) rate of annual increase, and an expan- sion of this species into the Nebraska Sandhills from South Dakota’s nearby breeding population at LaCreek Na- tional Wildlife Refuge would not be surprising.
The first statewide breeding-bird surveys were done in Nebraska dur- ing the 1980s (1984–89) and were published in 2001 (Mollhoff, 2001). These surveys involved the study of 443 survey blocks (each three miles square) involving every county. Two decades later, a second survey, cover- ing the field-work years 2006–11 and including 557 survey blocks, was un- dertaken (Mollhoff, 2016). Note that when comparing total confirmed nest- ings between the two surveys this ap- proximate 25% increase in survey sample sizes should be taken into con- sideration. Additionally, the number of hours of observer time per block increased by an average of 31% dur- ing the second survey, probably signif- icantly increasing the probabilities of species encounters.
The 2016 survey summary includes species accounts of all Nebraska’s 204 then-proven currently breeding birds, and an additional 18 probable nesting species. In the first atlas, 191 species accounts of proven breeders were in-
cluded, while in the second atlas 225 species accounts were provided.
During the 16 years between the two surveys, seven species were added to the state’s list of breeding species (Mississippi kite, snowy plo- ver, Eurasian collared-dove, white- winged dove, pileated woodpecker, Savannah sparrow, and Henslow’s sparrow), and three additional spe- cies were established as breeders dur- ing the second atlasing surveys (ash- throated flycatcher, sage thrasher, and lesser goldfinch).
The least frequently documented known or presumptive Nebraska breeders appearing in the state’s sec- ond breeding birds survey were (in ascending sequence of block occur- rences): the gray partridge, Clark’s grebe, snowy plover, Lewis’s wood- pecker, prothonotary warbler, com- mon merganser, chestnut-collared longspur, lesser goldfinch, mountain plover, cerulean warbler, common gal- linule, and sage thrasher.
The second survey’s most fre- quently reported Nebraska breed- ers (in descending sequence of block occurrences) were the morning dove, brown-headed cowbird, east- ern kingbird, red-winged blackbird, barn swallow, American robin, or- chard oriole, common grackle, west- ern meadowlark, killdeer, brown thrasher, red-tailed hawk, and Eu- ropean starling. Compared with the first Nebraska survey of the 1980s, the eastern meadowlark had dropped from being the fourth most-reported species to the ninth, whereas the brown-headed cowbird rose from be- ing the seventh most-reported spe- cies to the second. Two species, the
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mourning dove and eastern kingbird, retained their respective first- and third-place positions.
Species that increased most strongly in their relative breeding season presence, as judged by the differing number of counties (out of the 93 total) in which they were en- countered between the two surveys included the Eurasian collared-dove (86), Canada goose (57), house finch (57), tree swallow (53), bald eagle (44), Cooper’s hawk (43), red-eyed vireo (36), song sparrow (32), cedar waxwing (31), great-tailed grackle (29), vesper sparrow (28), wild tur- key (27), sedge wren (24), white- faced ibis (23), willow flycatcher (23), and blue-gray gnatcatcher (23). Species that decreased most strongly by the reduced number of counties of occurrence in the second of the two surveys included the black-billed cuckoo (35), black-billed magpie (29), eastern screech-owl (19), black- capped chickadee (15), lark bunting (12), northern pintail (11), and com- mon nighthawk (10).
Comparing the data from the 443 blocks surveyed during both survey periods, and including only those spe- cies for which there were at least 100 block occurrences during each of the two periods, the most apparently in- creasing species, based on percentage increase of total block occurrences in the second of the two survey peri- ods were the turkey vulture (144%), wild turkey (133%), chipping spar- row (131%), eastern phoebe (84%), eastern bluebird (76%), blue gros- beak (68%), red-tailed hawk (61%), red-bellied woodpecker (58%), Bell’s vireo (50%), horned lark (43%),
northern cardinal (43%), cliff swal- low (41%), great crested flycatcher (35%), lark sparrow (28%), bobolink (28%), yellow warbler (26%), great blue heron (25%), American kes- trel (24%), European starling (19%), wood duck (19%), field sparrow (19%), blue-winged teal (19%), grass- hopper sparrow (18%), dickcissel (17%), warbling vireo (17%), orchard oriole (16%), rock pigeon (15%), gray catbird (15%), white-breasted nut- hatch (15%), indigo bunting (14%), downy woodpecker (14%), northern flicker (12%), brown thrasher (10%), rose-breasted grosbeak (10%), up- land sandpiper (9%), mallard (8%), western kingbird (7%), brown-headed cowbird (7%), ring-necked pheas- ant (6%), house wren (6%), killdeer (5%), northern rough-winged swal- low (5%), American robin (4%), and American goldfinch (4%).
By the same criteria, the most ap- parently decreasing species as mea- sured by comparing percentage dif- ferences in total block occurrences between the two surveys were lark bunting (35%), loggerhead shrike (24%), yellow-billed cuckoo (18%), belted kingfisher (13%), chimney swift (8%), great horned owl (7%), house sparrow (6%), common night- hawk (4%), western meadowlark (4%), northern bobwhite (3%), Swainson’s hawk (3%), blue jay (2%), American crow (2%), and common yellowthroat (2%).
It should be apparent that because of (1) the 20% increase in geographic coverage during the second survey, and (2) the 31% increase in number of hours of observer time per sur- vey block, the estimated population
changes during the approximate two- decade interval between surveys are exaggerated both by the increased percentage of total blocks surveyed and the increased amount of observer time per block. Thus, these estimates of population changes of any seem- ingly increasing species should be reduced by about 55%, whereas the estimated population changes of any seemingly decreasing species should
be increased by about 55%. Thus, for example, by these criteria the breed- ing Nebraska turkey vulture popula- tion may have increased about 78% (rather than 142%) during the two decades between the two survey pe- riods, or about 4% annually, and the black-capped chickadee popu- lation may have declined by about 21% (rather than 39%), or about 1% annually.