The Changing Insect Fauna of Albany's Pine Barrens
by
Tim L. McCabe
New York State Museum
The Changing Insect Fauna of Albany's Pine Barrens | ||
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by Tim L. McCabe New York State Museum |
| Sand plains and similar inland sand deposits are desertlike islands in a sea of moist land. Because of rapid drainage of rainwater, sand plains are modern-day refugia that represent drier conditions that have existed off and on during the past 10,000 years. Drainage makes for drier soils that mimic prairie conditions and consequently harbor prairie relicts; thus these communities support a specialized flora and fauna. Sand barrens abound with rare or endemic forms, many of which are endangered. | ||
| The Albany pine barrens is a sand plains community and one of a relatively few scrub-oak (Quercus ilicifolia), pitch-pine (Pinus rigida) communities. Around the turn of the century, the Albany pine barrens was the site of intensive collecting by museum entomologists. Consequently, it has a historically well-documented and diverse insect fauna, making it possible to compare the fauna after a century of transition. Today, the region is heavily urbanized, and only 15.5 km2 (6 mi2) of the original 104 km2 (40 mi2) of natural barrens remain. As this habitat has been lost, 31 species of butterflies, moths, and skippers (Lepidoptera) have become locally extinct during the last century (McCabe et al. 1993). The past two decades have witnessed the most rapid change to the Albany pine barrens as well as the most dramatic decline of its resident insects. | ||
Insect Surveys and Data Collection |
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| A general survey of all insect species included collections made using malaise traps, light traps, and netting. Because pine barren communities require regular disturbance regimes (e.g., fire) to maintain the unique open habitats that characterize them, we evaluated insects in areas that had been recently burned. Postburn sites of 1, 5, 12, and 30 years of age were sampled. I gathered published records from numerous sources and, through comparison with recent catalogs and museum holdings, I attempted to identify those species that have a restricted distribution or at least are unusual for New York State (McCabe et al. 1993). The population of the Karner blue butterfly (Lycaeides melissa samuelis) was the focus of an intensive monitoring program using a visual transect method (Higgins et al. 1991; McCabe et al. 1993; Meyer and McCabe 1993). Better known and easily identified groups have also been evaluated (McCabe and Huether 1985 [1986]; McCabe 1985; McCabe et al. 1993; McCabe and C. Weber, unpublished data). | ||
Changes in Species Composition |
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| The species at the margins of their distribution in Albany have witnessed losses almost equally divided between north and south, suggesting that regular "pulses" of an insect species' distribution account for more species losses than can be attributed to the nearly seven-fold loss of habitat. It therefore seems appropriate to look closer at those species whose decline is most relevant to habitat loss. | ||
| The owlets Psectraglaea carnosa and Chaetaglaea cerata are usually found in coastal heath habitats but have been recorded from Albany. Chaetaglaea cerata is at precariously low levels in Albany, and P. carnosa is now locally extinct. Recent records of C. cerata and the last reports of P. carnosa were from an area of the pine barrens adjacent to the current landfill. | ||
| Another once-common species in the pine barrens is the owlet Homohadena badistriga, but I have observed this moth only once during the last 4 years (1989-93). Homohadena badi-striga caterpillars show a marked preference for the native shrub Lonicera dioica over all other Lonicera in the area. This shrub species, which appears to be a favorite browse of deer (personal observation), has become far less abundant in the past 12 years (J. Mattox, Bard College, personal communication). None of 27 bushes of L. dioica I had visited in 1982 exist today. | ||
| The owlet Agrotis stigmosa, which favors the periphery of open dunes, has a simpler story. The two most substantial open dunes in the Albany barrens have recently been developed, and A. stigmosa has subsequently been rarely encountered and may soon be lost. | ||
| The Karner blue butterfly (Lycaeides melissa samuelis), now listed as an endangered species, has markedly declined in the Albany barrens (Figure). This species appears to be a barrens relict that has been losing ground over all of the Northeast. Its larvae feed on Lupinus perennis (lupine). Another lycaenid butterfly, Incisalia irus, also dependent on lupine, has suffered a similar decline. The continued decline of L. melissa samuelis on the Albany pine plains (Figure) is illustrated by using both recent data (Higgins et al. 1991; Meyer and McCabe 1993) and earlier population estimates of Cryan (1980) and Schweitzer (1988, 1990). This downward trend continues even though some sites now support more lupine than a decade ago and appear to be well protected. |
Figure. Decline of the Karner blue butterfly at Willow Avenue site in Albany (McCabe et al.1993). |
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Pine Barrens Management |
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| Native pine barrens plants such as pitch pines, New Jersey tea, and lupine are very difficult to establish successfully. Seedlings are shaded out by scrub oak. Young pitch pines are heavily browsed by deer and severely attacked by an introduced pine sawfly; younger plants are completely defoliated. Lupines are devoured by cottontail rabbits. Most characteristic pine barrens plants require open, disturbed sites. | ||
| Fire has been scientifically employed as a management practice on the Albany barrens only quite recently. Scrub oak successfully regenerates after burns, as does the locust, Robinia pseudoacacia, a tree introduced from the Southeast for fence posts. One of the pine barrens rarities is Chytonix sensilis, a fungus-feeding moth. The year after a burn, fire-blackened trunks support luxurious growths of this fungus. Despite this, C. sensilis was most abundant in 12-year-old burn sites where hardly any fungus had been present. In areas unburned for more than 30 years, only C. sensilis females were collected. One 12-year-old site is the same one that supports Chaetaglaea cerata and had supported P. carnosa, suggesting that a burn frequency of at least 12 years is best to promote some of the choicest pine barrens associates. I trapped moths extensively in postburn sites of 1, 5, 12, and 30 years of age. No site was available with a postburn age between 12 and 30 years; an optimal burn frequency will likely fall somewhere within this range. A frequent burn schedule would be highly detrimental to insect species very susceptible to fires, such as one of the elfin butterflies, Incisalia henrici. | ||
| Species on the periphery of their range may not be reliable indicators of habitat quality. Natural fluctuation in range limits appears more significant than formerly considered. This can be attested to by the extirpation of 31, and the addition of 32, moth species. The decline of characteristic pine barrens species has to be examined on a case-by-case basis. | ||
| The Albany pine barrens has also been adversely affected by vehicular traffic, windbreaks created by roads and buildings, development of open dunes, introductions of exotic species, and even the frequency of fires, which promote some and compromise other pine barren rarities. Cutting to create oak openings should be considered as a management practice. In addition, open dunes may have to be artificially maintained where artificial windbreaks interfere. | ||
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New York State Museum The State Education Department University of the State of New York Albany, NY 12230 |
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| References | |
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Cryan, J.F. 1980. The Karner blue butterfly (Lycaeides melissa samuelis Nabokov) in the Hudson Valley sand belt of New York. Part 2. An annotated list of Hudson Valley sand belt populations and their status. A report for the New York State Department of Environmental Conservation. Higgins, L.E., T.L. McCabe, A. Meyer, and M. Rusch. 1991. Albany pine bush preserve--1991 entomological report. Prepared for The Nature Conservancy and the City of Albany, NY. McCabe, T.L. 1985. An annotated list of pine bush caddis (Insecta: Trichoptera). Skenectada 3:17-18. McCabe, T.L., and J.P. Huether. 1985[1986]. An annotated list of pine bush Cerambycidae (Insecta: Coleoptera). Skenectada 3:19-23. |
McCabe, T., A. Meyer, C. Weber, and L. Higgins. 1993. Albany pine bush project 1991-1992 entomological report. Submitted to the Eastern New York Chapter of The Nature Conservancy. 111 pp. Meyer, A.M., and T.L. McCabe. 1993. Albany pine bush project. Karner blue butterfly report. The Nature Conservancy. Unpublished report. Schweitzer, D.F. 1988. Supplement to 1988 Karner blue population studies: the Crossgates Mall population. A consultant's report to the City of Albany, NY. Unpublished report. 5 pp. Schweitzer, D.F. 1990. The 1990 status of selected Karner blue remnants in Saratoga and Albany counties, New York, with a discussion of monitoring methods. New York Department of Environmental Conservation, Endangered Species Unit. |