Birds and Drought: Winter Birds

In a grassland-oak savannah in southeastern Arizona, Carl and Jane Bock found that ground-foraging, seed-eating birds were 3 times more abundant one year after a 2-year drought ended than in the previous winter. Details from their abstract:

As a group, 19 species of ground-foraging, seed-eating birds (e.g., doves, quail, sparrows, towhees) were 2.7 times more abundant on the exclosure than on adjacent grazed grasslands during the first winter. These same species were 1.7 times more abundant on the exclosure during the second winter and were 2.9 times more abundant on both sites combined after the drought had ended. A second group of 24 avian species with different foraging ecologies (e.g., predators, frugivores, arboreal insectivores) did not differ between treatments or years. High-density, short-duration rotational grazing, coupled with a drought, left the land in a substantially denuded condition through two winters and negatively affected a variety of resident and migratory birds dependent on ground cover and seed production for over-winter survival.

Source:

Bock, Carl E., and Jane H. Bock. 1999. Response of winter birds to drought and short-duration grazing in southeastern Arizona. Conservation Biology 13: 1117-1123. URL: http://onlinelibrary.wiley.com/doi/10.1046/j.1523-1739.1999.98313.x/abstract [Abstract only]

Birds and Drought: Lower Klamath Refuge

The Lower Klamath National Wildlife Refuge, established by President Theodore Roosevelt in 1908 as the first refuge for waterfowl in the United States, encompasses an area of nearly 54,000 acres straddling the California-Oregon border.

According to refuge manager Ron Cole, water conditions on the refuge are "the driest on record since the 1940’s, as evidenced by mud flats, cracks in the mud and miles of barren wetlands."

In a typical year, upwards of 80 percent of the migratory waterfowl traveling the Pacific Flyway will use various units of the Klamath Basin refuge complex, with the majority of those individuals using Lower Klamath. But being “such a terrible year for water,” this is far from a typical year.

A request to the Bureau of Reclamation for 15,000 acre-feet of water, enough to flood 5,000 acres of the refuge’s seasonal marsh and provide habitat for upward of a half-million waterfowl, is unlikely to be fulfilled. Under the priority system governing the distribution of water in the Klamath Basin, endangered species are first in line, followed by Tribal subsistence fisheries and farmers. Only after these users receive their full allotments will any remaining water be made available for refuge use.

It seems certain that whatever water becomes available for the Lower Klamath refuge this year, it will be substantially less than what is needed to provide adequate feeding habitat for migratory waterfowl.

Birds and Drought: Crop Damage

In the wake of a drier-than-normal summer—with some areas experiencing a rainfall deficit of 5 or 6 inches—the Pennsylvania Department of Environmental Protection has issued a drought warning for 24 counties, and a drought watch for 43 more.
http://citizensvoice.com/news/dep-issues-drought-warning-for-county-1.1017885

Among the problems caused by the drought were reports of crop damage caused by birds. Ted Dymond, the owner of Dymond Farms in Luzerne County’s Franklin Township, had this to say:

The biggest problem we had, the dry weather created a shortage of moisture for birds. We had a lot of bird damage this year, and I kind of relate that to the drought.

This anecdotal report fails to identify the crops damaged (cucumbers and beans are mentioned in the context of the report, but neither is specifically identified as a crop damaged by birds), the type or extent of damages, or the species of bird(s) responsible for damages.

Birds and Drought: Palila Follow-Up

As a follow-up to my previous post about the Palila (an Endangered Hawaiian honeycreeper) and drought, I here present quantitative data on the impact of drought on Palila breeding efforts.

Lindsey et al. (1995) presented the results of a 7-year (1987-1993) study of annual survival, age, and sex ratios of the Palila on Mauna Kea, and offered the following observations on the impacts of drought:

The number of nesting attempts by Palila appeared to be influenced by annual differences in precipitation and differences in the availability of immature mamane pods [the principal food source] prior to and during the Palila breeding season (van Riper 1980; P. Banko, unpubl. data). For example, we located 71 Palila nests in our study area during 1991, a year of relatively high mamane pod production, compared to 52 nests during the previous year when mamane pods were moderately available (T. Pratt, unpubl. data). In 1992, when the drought caused an almost complete failure in the mamane crop, we located only five Palila nests [a 92 percent reduction from the average of the previous 2 years]. Adult Palila had higher survival in years when mamane production [and presumably precipitation] was relatively high.

"Hawaii is suffering through an unprecedented drought", with El Nino conditions the last two years having "added new misery to a half-century of declining rainfall on the tropical island chain."

Firefighters fear that "extreme wildfires could destroy native ecosystems and create devastating long-term environmental damage."

Sources:
Lindsey, G. D., S. G. Fancy, M. H. Reynolds, T. K. Pratt, K. A. Wilson, P. C. Banko, and J. D. Jacobi. 1995. Population structure and survival of the Palila. Condor 97: 528-535. URL:
http://elibrary.unm.edu/sora/Condor/files/issues/v097n02/p0528-p0535.pdf

van Riper, C., III. 1980b. The phenology of the dry-land forests of Mauna Kea, Hawaii, and the impact of recent environmental perturbations. Biotropica 12: 282-291. URL: http://www.jstor.org/pss/2387700 [Abstract only]

Birds and Drought: Palila

The Palila (Loxioides bailleui), an Endangered forest bird endemic to the “big island” of Hawaii, has declined 75 percent since 2003, to a population of 1,200 birds in 2010.

Photo credit: U.S. Geological Survey.

According to government officials, the Palila’s fate is due to a combination of factors:

impacts of feral goats and sheep (ungulates) on the mamane trees that the birds depend on for much of their diet,

effects of severe drought on the bird’s food supply, and

predation by nonnative feral cats.

In response to the crisis, conservation agencies have proposed a monumental project to erect a fence encircling the entirety of the designated Critical Habitat for Palila on Mauna Kea, with the goal of excluding exotic ungulates from the area.

Drought, Beetles, Jays, and Nutcrackers in the American West

From the Cornell Lab of Ornithology’s Project FeederWatch comes a fascinating tale about how Pinyon Jays and Clark’s Nutcrackers dispersed widely in the winter of 2002-2003 in response to a protracted drought that had prevailed in the southwestern U.S. since about 1999. The drought, in combination with infestations of native beetles that resulted in the widespread loss of Pinyon Pines, a valuable food source, caused the birds to wander in search of alternative foods.

Drought and Birds: Mallard

Gary L. Krapu, Albert T. Klett, and Dennis G. Jorde (1983) studied reproductive strategies of Mallards breeding in the prairie pothole region of North Dakota under the variable spring water conditions characteristic of that region. Specifically, they examined "population patterns in eastern and central North Dakota over a 20-year period and examined factors responsible for observed densities and reproductive effort under a broad range of wetland habitat conditions."

In summarizing the results of this important study, I can do no better than provide the authors’ Abstract in full:

Mallard (Anas platyrhynchos) breeding densities in the prairie pothole habitat of eastern North Dakota during 1961-1980 varied from 2.28 birds/km2 in 1977 to 9.47 birds/km2 in 1963 [a factor of 4.2] and were correlated with pond abundance (r = 0.543, P < 0.05). The number of basins used by pairs declined with drought, as did home-range size. Nesting activity also varied with the number of ponds holding water/km2, ranging from high (including substantial renesting) under favorable water conditions to low during extreme drought. The span between first and last nest initiations declined by 19 days from a wet to a dry year. With severe drought conditions during spring 1977 on the Medina Study Area, pairs returned to attempt nesting but were unsuccessful, and most abandoned activity centers by mid-May. Although the average clutch size declined by about 0.7 egg[s] from a wet to a dry year on the Interstate Study Area, hatchability of eggs remained constant. We describe the adaptive strategy of Mallards for breeding under variable water conditions and food resources in the semiarid environment of mid-continent North America.

Thanks to SORA (the Searchable Ornithological Research Archive) this paper may be read in full by clicking on the title highlighted below.

Citation:

Krapu, Gary L., Albert T. Klett, and Dennis G. Jorde. 1983. The effect of variable spring water conditions on Mallard reproduction. Auk 100: 689-698. [.PDF]

Drought and Birds: Avocets and Stilts

The complex of wetlands in the Lahontan Valley of Nevada, designated as a Hemispheric Reserve within the Western Hemisphere Shorebird Reserve Network in 1988, declined in area from 34,800 hectares in 1905 to 6,150 hectares in 1987, a net loss of 82 percent.

Julia A R. Alberico (1993) studied the breeding biology of American Avocets (Recurvirostra americana) and Black-necked Stilts (Himantopus mexicanus) in the Lahontan Valley in the drought year of 1991 and reported the results in Western Birds.

Her Summary:

I monitored breeding American Avocets and Black-necked Stilts in the Lahontan Valley, Nevada, during the fifth year of drought. There were few sites suitable for breeding, and at sites where birds did breed, nest depredation was extremely high. In a non-drought year there would be thousands of breeding recurvirostrids in the area I monitored; in 1991 there were fewer than 100. Only six pairs of stilts hatched chicks, and avocets failed entirely.

Nest predation pressure is probably higher in drought years because nests are more accessible to coyotes, and duck eggs and other prey items for ravens are limited. Antipredator behaviors seemed ineffective under such pressure.

In areas where 1,000, and often as many as 4,000, young avocets and equal numbers of stilts were routinely produced in each of the 18 years monitored between 1949 and 1975, Alberico documented no avocet chicks and just 21 stilt chicks.

Alberico cites others to the effect that recurvirostrid populations declined in the Lahontin Valley during the dry years of 1976 and 1977, while simultaneously increasing at Great Basin wetlands in Oregon and Utah, "suggesting they had moved from drought-stricken areas such as the Lahontan Valley."

Of 59 avocet and 10 stilt nests at one site (Mahala Slough) in 1991, 13 avocet nests (22 percent) were depredated by coyotes (Canis latrans) and 42 avocet nests (71 percent) and 2 stilt nests (20 percent) were depredated by birds. Common Ravens (Corvus corax) were the primary avian nest predators, although California Gulls (Larus californicus) may also have been involved occasionally.

Alberico comments about the effects of the drought on predation:

Several conditions associated with drought might have increased nest vulnerability and predation rates on recurvirostrid nests in the Lahontan Valley. As Mahala Slough dried up, I observed (from tracks and direct sightings) increasing coyote traffic around nesting areas, coupled with an increase in nest predation by coyotes. As the ponds dried up, nests initiated on hummocks surrounded by water soon became accessible via land or by shallow wading.

More specifically, she found that "Stilt nesting success was related to water depth, as five of six successful nests were surrounded by water deeper than 0.75 m."

Also, "A drought-induced shortage of typical prey items [especially nesting waterfowl] may have prompted ravens to increase their predation on avocet and stilt eggs."

Alberico’s article can be read in full by clicking on the highlighted title below.

Citation:

Alberico, Julie A. R. 1993. Drought and predation cause avocet and stilt breeding failure in Nevada. Western Birds 24: 43-51. [.PDF]

Drought and Birds: Snail Kite

In one of the first Federally-funded field studies of an Endangered species in the United States, Paul W. Sykes Jr. (1979) examined population status, nesting success, and movements of the Snail Kite (Rhostrhamus sociabilis plumbeus)—formerly known as the Everglade Kite—in the human-altered marshes of south Florida over a span of 11 years, 1968-1978. The bill of the Snail Kite is uniquely adapted for feeding almost exclusively on apple snails (Pomacea sp.), which makes them wetland obligates, and thus particularly susceptible to drought.

Drought-related impacts on Snail Kites are emphasized in this excerpt from Sykes’s Summary:

The severe drought of 1971 resulted in a significant decrease in the population for that year and 1972, with no nesting attempts being observed in the dry year. From 1974 through 1978 the population increased significantly (r = 0.92, P < 0.025), apparently the result of favorable water conditions and increased food supply. The loss of suitable habitat is the major problem facing the species in Florida. A high water level is essential, as it affects food supply and its availability, as well as nesting success.

More specifically, in the two drought-influenced years (1971-1972), nesting attempts and number of young fledged were reduced to 3 and 1.5/year, respectively. By contrast, these same variables averaged 15 and 16/year in three pre-drought years (1968-1970) and 33 and 26/year in four post-drought years (1973-1976). In other words, drought conditions reduced nesting attempts to 20 and 9 percent of pre- and post-drought levels, and number of young fledged to 9 and 6 percent of pre- and post-drought levels.

Regarding population movements, Sykes notes: "My field work, beginning in 1967, has shown that kites are nomadic in Florida. Since widespread water manipulation has affected their food supply, kites must be nomadic to survive." Sykes concludes that "The nomadic behavior exhibited by this kite in recent years, probably represents a normal response to changes in water levels and food availability."

In discussing mortality, Sykes adds that "some individuals probably starved in drier years."

Additional details are revealed in the Discussion:

Each year, following breeding, some birds disperse, but during the drought of 1971 they were scattered more widely than usual over the entire Florida peninsula. The reduced food supply resulting from dry conditions apparently raised the mortality rate. In 1971 there was no recruitment to the population and when the census was taken only 72 individuals could be found. Although dispersal might have affected the actual number of birds seen, it was obvious that the population had decreased. In 1972 nesting attempts were at least 60% below the 1968—1970 period, and only 65 individuals were recorded on the census. Dry conditions prevailed in 1974 and there was a corresponding decrease in the kite population (Figure 4).

Sykes’s article can be read in full by clicking on the highlighted title below.

Citation:

Sykes, Paul W., Jr. 1979. Status of the Everglade Kite in Florida—1968-1978. Wilson Bulletin 91: 495-652. [.PDF]

Drought and Birds: Dew Bathing

Early on the morning of August 26, 1961, Nicolaas A. M. Verbeek (1962) observed 29 individuals of 7 species bathing and washing themselves in the dew that had gathered on the leaves of a shrubby vine maple (Acer circinatum) near Vancouver, British Columbia. Engaged in this behavior were 2 Red-eyed Vireos Vireo olivaceus, 15 Black-capped Chickadees Poicele atricapillus, 2 Golden-crowned Kinglets Regulus satrapa, 7 Orange-crowned Warblers Vermivora celata, 1 Black-throated Gray Warbler Dendroica nigrescens, 1 Wilson’s Warbler Wilsonia pusilla, and 1 Song Sparrow Melospiza melodia.

Verbeek attributed this rarely observed or reported behavior to the local drought conditions prevailing at the time, “with only a little over a centimeter [0.39 inches] of rain recorded in the 50 days preceding the day of observation.” While July and August are typically the driest months of the year in Vancouver, an average of 7.87 centimeters (3.1 inches) of rain normally falls during that period, nearly 8 times the amount recorded in 1961.

While others have reported instances of dew bathing in the wild (see Nichols 1921, Abbot 1954, Douglas 1968, and Baptista 1973), Verbeek is the only one who has suggested a connection between this behavior and drought. It seems likely that dew bathing would be more common amongst species that inhabit arid regions. In fact, Jim Conrad reported his observation of Yellow-rumped Warblers Dendroica coronata and Clay-colored Sparrows Spizella pallida bathing in the dew that had collected on mesquite leaves in northern Chihuahua.

Verbeek’s article, as well as the other references, can be read in full by clicking on the highlighted titles below (all are in .PDF format).

Citations:

Abbot, Waldo G. 1954. Leaf bathing of the Mockingbird. Condor 56: 163-164.

Baptista, Luis F. 1973. Leaf bathing in three species of emberizines. Wilson Bulletin 85: 346-347.

Dow, Douglas D. 1968. Dew bathing and related behavior of the Cardinal. Bird-Banding 39: 227-228.

Nichols, J. T. 1921. Coereba bahamensis at Miami, Fla. Auk 38: 461-462.
http://elibrary.unm.edu/sora/Auk/v038n03/p0461-p0462.pdf

Verbeek, Nicolaas A. M. 1962. On dew bathing and drought in passerines. Auk 79: 719.

Drought and Birds: Introduction

Birds must deal daily with a host of weather variables, be it rain, snow, sleet, hail, lightning, tornadoes, hurricanes, or temperature extremes. One of the longer-term climatic factors with which birds must periodically contend is drought, the lack of precipitation.

The Community Collaborative Rain, Hail, and Snow Network (CoCoRaHS)—in cooperation with the National Drought Mitigation Center and the National Integrated Drought Information System—has asked its national network of observers to begin submitting reports of how their communities have been impacted by drought.

The CoCoRaHS "Drought Impact Reporting Guide" can be viewed at this slideshow.

Spurred by this interest in drought, I will endeavor to periodically summarize information about the impact of drought on birds, particularly in North America. My primary source of information will be the invaluable treasure-trove of ornithological literature available through SORA, the Searchable Ornithological Research Archive.

Stay tuned!