|No. 187||BATON ROUGE, LA||September 1999|
Louisiana Birds- Spring Migration 1999
July Pelagic Report
Deserving Young Birder
LA Black Skimmers
Calidris Figure 1
Calidris Figure 2
Calidris Figure 3
Calidris Figure 4
Doug Pratt Award
The Botanical Birder
LOS NEWS, page 1
Birds After Birders
LA Green Violet-ear
1999 LOS Fall Meeting
Welcome New Members
Sabine Pass Lighthouse
Trans-Gulf Migration Project
Swainson's Warbler Project
"Peep" is a word loosely used to refer to sandpipers in the genus Calidris. The genuscontains small to medium-sized shorebirds ("sandpipers" in the New World; "stints" in the Old World). Ten species regularly occur in Louisiana: Red Knot (Calidris canutus), Sanderling (C. alba), Semipalmated Sandpiper (C. pusillus), Western Sandpiper (C. mauri), Least Sandpiper (C. minutilla), White-rumped Sandpiper (C. fuscicollis), Baird's Sandpiper (C. bairdii), Pectoral Sandpiper (C. melanotos), Dunlin (C. alpina), and Stilt Sandpiper (C. himantopus). All these species migrate through Louisiana to breeding areas in the Arctic. Timing of migration and routes vary between species. A few species regularly winter, the remaining species winter farther south. Two additional species occur as vagrants: Curlew Sandpiper (C. ferruginea) and Purple Sandpiper (C. maritima). Another two species have been documented as close to Louisiana as Texas: Red-necked Stint (C. ruficollis) and Sharp-tailed Sandpiper (C. acuminata) and are eagerly anticipated vagrants!
Approaching Calidris identificationPeeps and other shorebirds feed on insects and other invertebrates caught at or below the surface of the ground, usually in shallow water or rich mudflats where these organisms abound. In Louisiana, the most productive shorebird sites are coastal estuaries, beaches, and especially, inland habitats (mudflats and shallowly flooded impoundments) created by rice andcrawfish culture. Rich habitats may support high densities of birds at a single time. Because these habitats are often ephemeral in nature, shorebirds concentrate in prime spots. During migration peeps locate the most productive habitats and form huge multi-species flocks ofpeeps and other shorebird species. The thought of identifying particular individuals among such assemblages of similar-appearing birds can be overwhelming.
The first three steps to shorebird identification begin before you go into the field. We recommend that you 1) determine which species are most likely to be present at a particular place and time. Figures 1 and 2 are annotated bar graphs for Calidris and are intended as preliminarly updates of those in Louisiana Birds (Lowery 1974). The bar graphs are a compilation of reports/data spanning over 30 years of field observations. Most future sightings will fit into the patterns illustrated. Observations that fall outside the illustrated patterns should be submitted to LSUMNS and should be accompanied by written details of the observation. The graphs give relative abundance through the year. Note that there are a few species that are absent during part of the year; it is extremely unlikely that you will encounter individuals of these species during this period. Such a find is equivalent to finding a vagrant. For example, you are probably more likely to find a vagrant Purple Sandpiper in late winter, than a Semipalmated Sandpiper, a species that is an abundant spring and fall migrant! Be prepared to document extraordinary out-of-season records (as indicated by a gap in the bar graph) as you would a vagrant. After you determine which species should be present (and thus, narrow down the possibilities), 2) familiarize yourself with the basic species-specific "field marks." Field observation is easier, more enjoyable, and certainly more satisfying, if you know what species you might encounter and the general "basics" on how to identify those species. Because shorebirds have multiple plumages and the appearance of birds "between plumages" can be a little confusing, a 3) general understanding of shorebird plumages will help you better unravel a bird's identity. If you know what marks are important and a possible range of variation of plumage appearances, you should be able to identify most birds in the field. More field time can then be spent studying the birds, instead of flipping back and forth through your field guide trying to figure out the "basics." However, definitely consult your guide for assistance in the field, or to confirm your identification. We recommend National Geographic Society Fieldguide to Birds of North America (NGS) for shorebird ID information in a (and best to date) general guide. NGS fairly accurately illustrates important plumages (alternate, basic, and juvenal) for each species, as well as noting main identification criteria and vocalizations. The NGS Third Edition has replaced three of the six plates that containthe following peeps: pg. 173 (knots, Dunlin, Sanderling); pg. 179 (Pectoral Sandpiper); and pg. 183 (Stilt Sandpiper). Although we recommend NGS over other field guides currently available, NGS has still devoted relatively little space to the peep identification. The brevity and simplicity of the accounts may confuse beginning, as well as intermediate, birders. For instance, there is no mention of sexual size dimorphism or its role in identification. We further recommend Shorebirds, an Identification Guide (Hayman, Marchant, and Prater 1986). The additional information (and lovely illustrations) will help piece-together what's missing in NGS. Shorebirds covers all of the world's shorebirds and should be added to every birder's library. A Guide to the identification and ageing of Holarctic Waders (Prater, Marchant, Vuorinen 1977) provides concise accounts of aging criteria for those specifically interested in aging, and is also a helpful reference.
Now you are ready to go in the field! 4) When you arrive at a shorebird site, position shorebirds in good light, isolate a group to study, and try to approach the group to close distance where plumage patterns are clearly visible (a telescope is very handy). This is a very crucial step. A well-seen bird is a much easier-to-identify bird. So much of the frustration of identifying shorebirds can be avoided if you are "close-up and personal." 5)Focus on individual birds. This is to eliminate "flock syndrome," a condition that occurs when all members of a flock (shorebirds, gulls, ducks, etc.) blend together to form a single entity, with the assumption that "all birds are the same species." This is bad, because more than one species is often represented in a flock. 6) Force yourself to identify every bird. Study each bird's relative size, bill length and shape, and plumage details. It is at this point that individual variation and sexual dimorphism become apparent. Only after you have mastered the common species will you be properly prepared to search for vagrant species. Peepsfrequently vocalize and call notes are distinctive, so 7) listen to and learn vocalizations. Peeps make a variety of aggressive fussing notes ("geeeee-tee-ee-ee-ee-ee", etc.) in addition to their diagnostic calls. These calls are very similar between some Calidris (Western and Semipalmated sound essentially the same; Stilt Sandpiper is very different). Do not confuse these notes with the diagnostic single-note calls. Sometimes one or more birds will utter the call notes so that you hear a series of single notes, but these should still be easy to separate from the aggressive fussing notes. The field guides give interpretations of call notes, but we advise that you create your own "words" for these notes. It is much easier to remember your own renditions, especially if you do not agree with the field guide's version. Peepcalls are very helpful identification tools. It may be difficult to note subtle bill or plumage differences in flight on a swirling flock, but shorebirds will often announce their identification with their diagnostic calls. If you invest quality time with peeps, and familiarize yourself with the range of individual variation within species and know basic call notes, identification will become straightforward. You may even be able to identify those peeps under less ideal conditions. You can become a peep pro.
The importance of molt and wearMolt basics A lot of the mystery of seasonal plumage variation can be understood by reviewing the basics of molt. This is especially true for shorebirds; an understanding of the mechanics of molt will further aid in their identification. During molt (from Latin meaning "change"), a bird replaces most or all of its feathers. Old feathers are shed and are replaced by new ones that emerge through the skin. For most birds, feather replacement is a gradual process that may span a period of a couple of months. At the beginning of the molt, the bird is in only one plumage (e.g., breeding plumage). As the molt progresses, and feathers are replaced, the bird's appearance changes. Until molt is complete, a bird's appearance is a mixture of the two plumage types (Figure 3). The appearance change may be very subtle (e.g., sparrows with essentially only one plumage) or dramatic (e.g., breeding versus non-breeding plumages of some tanager or warbler species.) Field guides rarely depict birds in-between plumages even though the two plumages may be dramatically different.
There are two types of molt: complete (involves all feather tracts and areas of the body) and partial (involves specific feather tracts and areas of the body). The molt is named by the plumage it precedes (e.g., Alternate Plumage is acquired by the Pre-Alternate Molt). The number of molts varies per year depending on species. Timing and degree of molt may also vary with age, sex, geographic origin, and can be influenced by environmental conditions. The term "Definitive" refers to a plumage type that does not change with age (e.g., the "winter/non-breeding" plumage of an adult shorebird is a Definitive plumage). The names of plumages are standardized, so that plumages can be compared, even between species on very different breeding cycles in different parts of the world. The plumage following a complete molt (usually following the breeding) is referred to as the Basic Plumage (the "basic" plumage of all birds). A plumage acquired through molt and different from the Basic Plumage is an Alternate Plumage.
The exposed portion of a feather gradually abrades (wears) until it is replaced by the next molt. Feathers are "fresh" after a molt, but become "worn" through time. Lighter colored portions of feathers abrade faster than darker areas because they are not as strengthenedby pigment. Also, feathers protected by other feathers (bases), wear less than those completely exposed (edges) to the environment. Worn feathers may appear ragged, tattered, and even become bleached by the sun. Because the flight feathers are only replaced once a year (many species), wear on these feathers (especially primaries) is often conspicuous. To a certain point, wear (notably body feathers) may enhance the appearance of the overall plumage. Alternate plumage is enhanced by wear, if pale feather edges abrade and expose darker, more colorful feather centers. For that reason, birds in full alternate plumage observed earlier in thespring appear less colorful.
Shorebird molts and plumages Shorebirds have two molts per year. A complete molt that involves the replacement of all body and flight (wing and tail) feathers and a partial molt that involves all or part of the body feathers only, and does not include the flight (notably remiges = wing) feathers. Definitive Basic Plumage is acquired by a complete molt. The Pre-Basic Molt usually occurs after or near the completion of the breeding cycle. Peeps (as well as many other groups of birds) employ one of two Pre-Basic Molt strategies depending on the species: 1) molt takes place on the breeding grounds prior to migration; or 2) molt takes place on or near the wintering grounds upon completion of migration. This means that southboundmigrant shorebirds arrive in Louisiana in either worn alternate (molt strategy #2) or fresh basic plumage (molt strategy #1). Red Knot, Sanderling, Semipalmated, Western, Least, Pectoral, and Stilt sandpipers undergo their pre-basic molt on the wintering grounds (Strategy #2). Individuals of species that winter in or near Louisiana (Red Knot, Sanderling, Western, Least, and Stilt sandpipers) begin pre-basic molt shortly after their arrival. Therefore, these species can be observed in a mixture of two plumages shortly after the species' fall arrival. Whether some birds may linger and molt north of their final wintering destination is not known (e.g., do some Sanderlings do a partial molt in Louisiana before they continue south to winter in Peru?). Only Dunlin employs Molt Strategy #1; southbound Dunlins arrive in basic plumage. For this reason, Dunlins also arrive much later in the fall compared to the other species. Species that do not winter in Louisiana (Semipalmated and Pectoral sandpipers) are rarely observed in full basic plumage during fall migration. A peep's Definitive Alternate Plumage is attained by a partial molt in late winter or spring. This molt may take place on the wintering grounds or during migration.
The Juvenal Plumage is the first set of true (non-down) feathers worn by a bird. In shorebirds, this distinctive plumage is held only briefly, and is replaced by a partial molt (most species) on the wintering grounds. This molt involves only body (and no flight) feathers (at least for species that occur in Louisiana). Usually some of the juvenal feathers are not replaced during this molt, notably the inner medium coverts (shoulder). The retention of juvenal feathers allows a bird to be identified in First Basic Plumage, which would otherwise be indistinguishable from Definitive Basic Plumage. A juvenal's first "breeding" plumage is referred to as the First Alternate Plumage. Many birds are indistinguishable from adults at this point, whereas others only attain a partial breeding plumage during their first summer. The amount of feathers replaced during the pre-alternate molt varies; some individuals may remain essentially in basic plumage. Juvenal flight feathers become very worn during the late spring and early summer. During the summer, juvenals undergo their first complete molt to acquire Definitive Basic Plumage.
Temporal distribution: shorebird seasonsShorebirds occur in Louisiana during four "seasons": winter, spring, fall, and summer. "Shorebird seasons" refer to periods of movement (spring and fall migrations) or stasis (breeding/wintering). Depending on the species or individual "winter" may span from early July through mid-April! "Spring" may span a period beginning as early as late February and extend into mid-June. "Fall" may begin as early as the beginning of July and extend to early December. "Summer" may span from mid-April through mid-September.
Shorebird seasons vary by species. For instance, the majority of Pectoral Sandpipers move north in spring well before White-rumped Sandpipers. Timing may also vary with regard to sex and age. Male Pectoral Sandpipers are first to arrive in spring; adult Pectorals precede juvenals by nearly one month in the fall. The term "early" or "late" migrant is reserved for individuals that are at the extreme ends of the migration period, rather than as applied to a species as a whole (Pectoral vs. White-rumped sandpipers).
Sometimes it is difficult to pigeon-hole a particular bird to a season. Species that are represented in the state solely by migrants are more straightforward. For example, Semipalmated Sandpiper does not winter in the state so it is easy to spot the first northbound migrants of the spring. First spring records of Semipalmateds are in late March. The number of Semipalmateds peak during mid- to late April, then numbers drop off as the majority of birds have passed through the state. A few late migrants linger into early June. A few individuals may "summer" along the coast (see below). Fall migrants reappear in early July, peak during August and early September, and numbers then diminish with stragglers detected as late as early November. There are no accepted records of Semipalmated Sandpiper after mid-November.
For species that winter in Louisiana, it is difficult to differentiate between wintering birds, arrival of the first spring migrants, or the departure of the last fall migrants. Western Sandpiper, for example, is an abundant wintering species in the southern rice-growing areas of the state. In these areas it is difficult to pick out newly arriving spring migrants from wintering birds. During late winter and spring, birds in different stages of molt can be found, but status and point of origin are unknown. In areas where Western Sandpiper is not common in the winter (e.g., N Louisiana), detection of first northbound migrants is more straightforward, thus regional data are very important.
Some migratory shorebirds remain in Louisiana during the summer, ending their northward movement before reaching the breeding grounds. Some species of peep are regular in moderate numbers (e.g., Sanderling and Red Knot), whereas there are only a few records of other species such as White-rumped Sandpiper; Baird's Sandpiper has never been confirmed "summering." In general, species that regularly winter in Louisiana are more likely to "summer" in Louisiana. Most records of "summering" birds likely involve injured, sick, or immature birds that have migrated only a portion of the way to the breeding grounds or not at all. There is really only a short period of time between the last spring and the first fall migrants, so confirmation of a definite "summering" bird is really a "best guess." Unless an individual bird has been monitored at a particular site, it is difficult to know whether a particular bird has been present "all summer." This is also compounded by the ephemeral nature of potential summering habitat. It is difficult to know how "local" a bird has remained without actually marking the bird in some way. Some visual cues, based on your knowledge of timing of migration and molt, may provide some insight. Birds in partial alternate (or in basic plumage) with active wing (primary) molt are more likely summering. Birds generally do not embark on long distance movements with wing molt. Injured birds encountered during late spring periods when birds are not normally still migrating are also probably summering (after fall migrants arrive this is not a good separating feature). Alternate-plumaged Dunlins in July-August are likely summering, as southbound migrants arrive later and in basic plumage.
Migration routes and habitat preferencesMigration routes may also vary. For most species, individuals are present during both spring and fall migration. These species can be found over much of the state where suitable habitat occurs. There are a few exceptions. White-rumped Sandpiper is a common spring migrant, but completely bypasses Louisiana in the fall. From the Arctic breeding grounds, White-rumpeds move east and then south along the Eastern Seaboard; there are probably no true records of southbound migrants for Louisiana. In contrast to White-rumpeds, where all individuals follow the same fall route, adult and juvenal Baird's Sandpipers follow different routes. Adult Baird's Sandpiper is a relatively uncommon spring migrant; most northbound individuals travel north well west of the state. Larger numbers in spring often coincide with periods of strong westerly winds. On the return route, southbound adult Baird's stage on the prairies before making a nonstop flight to South America. Adult Baird's are rarely encountered here, there being only a confirmed few fall records. Juvenals, on the other hand, move south on a broad and more leisurely front and account for the majority of state records.
Generally, peeps prefer muddy habitats, but some generalizations can be made regarding habitat or micro-habitat choice of particular species. Regardless of these preferences, there can be complete overlap between species and preferred habitat depending on habitat (and food) availability. For instance, dry dirt fields are often preferred by Baird's Sandpiper. Other species generally don't forage on dry dirt, but it can happen (e.g., Least, Pectoral, Western, and Semipalmated sandpipers). Species may forage in different water depths. Dunlin and Stilt Sandpipers will forage belly-deep, rarely will other peeps forage in such deep water. Western Sandpipers generally forage in deeper water (but occasionally belly-deep) than do either Semipalmated or Least sandpipers that usually hug the water's edge. Purple Sandpipers are nearly always found on rocks, sometimes in the company of other rock-foragers (Sanderling, Least, and less commonly, Western sandpipers). Grassy edges, partially flooded rice, or weedy fields are preferred by Pectoral and Least sandpipers, but other species may occupy grassy fields if no other foraging areas are available.
In contrast to preferential segregation by habitat feeding sites, there are occasions where this system breaks down and large numbers of many species occupy an area of uniform habitat. Probably one of the best shorebird habitats in Louisiana is a manmade one: a nearly drawn-down crawfish pond. Shorebirds crowd in to feast upon invertebrates (insect larvae, worms, crustaceans, clams, etc.). Such a pond can also provide a variety of waterlevels and vegetative growth. Unfortunately, the overall crawfish crop cycle does not overlap with the peak fall migration of shorebirds (mid-August through late September). However, the occasional August-September crawfish pond draw-down is a spectacle to behold. In fall there is much less shorebird habitat in general, so birds are generally more densely packed into what habitat is available. The spring rice cultivation cycle provides many shorebird opportunities, the best situation being a graded field that is receiving the first flooding of the season. Shorebirds forage along the wet-dry interface until the water floods the field. When the water is drawn down prior to seeding and re-flooding, the shorebirds return to work-over the exposed mudflats.
ID pitfallsThe species pair that presents the greatest peep identification challenge in Louisiana is Semipalmated vs. Western sandpipers. In fact, Semipalmated Sandpiper was once thought to winter (see bar graphs, Lowery 1974). So similar are these species in basic plumage that small-billed Westerns were once assumed to be Semipalmateds! Though Semipalmated Sandpipers could occasionally winter, there are no confirmed records between mid-November and early March. All species of Calidris show slight to pronounced sexual dimorphism. In general, females average larger and longer-billed than males (Pectoral and Sharp-tailed sandpipers being the exception -- males average larger than females). This dimorphism is fairly dramatic with regard to bill size in Western Sandpiper (Figure 4). All illustrations of Western Sandpiper in the NGS guide depict the bill to be the same length. The illustrations are consistent witha female Western Sandpiper. In comparison, the bill illustrations for the Semipalmated are also all the same length. NGS does not illustrate overlap in bill length between the two species. Although the text mentions some variation in bill length (and shape), someone trying to identify a bird from the illustrations (as many do) could easily draw the wrong conclusion. The illustration of the basic-plumaged Semipalmated looks very much like a male Western, including the bill tip appearing slightly tapered and drooping.
Bill shape is the best way to separate Western and Semipalmated sandpipers in transitional or basic plumages. Shorebirds does a much better job describing the differences betweenthese two species; see also Figure 4. In alternate or juvenal plumages, there are plumage characters that will also provide clues to the identification of this species pair. The NGS illustrations of birds in alternate plumage are representative of the variation between the two species, but it is important to realize that many birds observed in LA are not necessarilyin full alternate plumage during spring migration (bright plumage is concealed earlier in the spring by dull-colored feather edges). The best distinguishing plumage character between these species in an intermediate (basic alternate) plumage is the presence of lower flank streaks or chevrons on Western Sandpipers. The only other species possessing this character is White-rumped Sandpiper. Birds in juvenal plumage are best separated by the presence of rust-edged feathers at the shoulder of Western Sandpiper.
Separation of other species of regularly-occurring peeps is no where as difficult as Western vs. Semipalmated sandpipers. Species that might be confused are: Baird's Sandpiper vs.Sanderling (in alternate plumages); Pectoral vs. Least (similar in plumage features and leg color, but very different size); and Dunlin vs. Stilt Sandpiper (in basic plumages). Although most experienced observers can readily distinguish between these species pairs, beginners might have some initial problems. Observations under less than ideal conditions usually result in misidentifications. A careful close view should make identification easy. Check the NGS guide for the best characters to separate these species pairs.
Donna L. Dittmann & Steven W. Cardiff
435 Pecan Drive
St. Gabriel, LA 70776
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|Doug Pratt Wins Edwards Prize|
Doug Pratt, of the LSUMNS, along with his co-authors, has been awarded the Edwards Prize for the best major paper in the Wilson Bulletin.. His winning paper, in Volumn 110, was "Reflections on a 1975 expedition to the lost world of the Alaka'i and other notes on the natural history, systematics, and conservation of Kaua'i birds."
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|The Botanical Birder|
The Good. The Bad, & the Poisonous
In the world of birds and humans, the phrase, "One man's meat is another man's (sic) poison," is nowhere more appropriate, for there are many instances of birds relishing fruits which are downright toxic to humans. One such example involves the fruits of poison ivy (Toxicodendron radicans). Upon initiating a casual study of bird frugivory habits in Louisiana about 15 years ago, I was quickly impressed at both the magnitude and diversity of poison ivy fruit predation within our regional avifauna. Looking back, I don't know why I should have been: the fruits are both conspicuous and abundant; and the plant itself enjoys one of the widest distributions throughout just about every conceivable habitat within our state. Much later, while reviewing avian frugivory literature, I was again caught off guard at Martin, Zim, &, Nelson's (1995, American Wildlife & Plants: A Guide to Wildlife Food Habits) compilation of fifty-six U.S. bird species known to utilize the fruits of this plant. Again, I don't know why such a figure should have surprised me, for by that time, several of us Louisiana observers had compiled our own list of twenty-three avian poison ivy users - all in a space of less than four years! Was it perhaps my own bias/disdain/fear working overtime against the pure, simple, and elegant logic that comes from direct observation? Whatever.
Poison ivy belongs to the Sumac family (Anacardiaceae), a fairly substantial plant group that contains approximately 60 genera and nearly 600 species, mostly limited in range to the New and Old World tropics. Here in the U.S., poison ivy itself is split into two species: eastern poison ivy (containing six subspecies), native from Texas northward to Minnesota and east to Maine and Florida, and western poison ivy (Toxicodendron rydbergii), native to the Pacific states. Additionally, most of Canada and Mexico are inhabited by various combinations of both species.
While it can occur as a shrub (infrequently) and a ground-cover (frequently), poison ivy is best known as a vine. Because of the fear and loathing that most people have for poison ivy, many other vine species are frequently mistaken for it - sort of like back in the 1950s when everyone temporarily thought everyone else was a communist. Here in Louisiana, Virginia creeper (Parthenocissus quinquefolia), pepper vine (Ambelopsis arborea), and trumpet creeper (Campsis radicans) are routinely misidentified as poison ivy. Like gulls, though, poison ivy can always be successfully separated from its closest look-alikes via a combination of characters. Poison ivy leaves are compound 3-foliate (like the toes on a gull [minus the webbing]); 5-foliate on very rare occasion. Shape of the terminal or middle leaflet, in general, is elliptic with a fairly pointed apex. Shape of the side leaflets is similar, but is most often differentiated with one large lobe near the base, like a thumb on a hand. The problem is that there is a tremendous amount of variability in leaflet size, shape, and extent of lobing. Too, poison ivy is a deciduous plant, so identification by foliage is not possible during the winter months. It's best to focus on the appearance of the vine/stem itself to cinch the identification, especially here in the lower South where the stems appear to be densely covered with dark-brown "hair" - a trait shared by no other vine in our region. These "hairs" are actually rootlets. As with humans, young/mature vines are thickly coated with them, while older vines gradually go "bald." Still, there are almost always at least a few clumps of rootlets remaining on even the oldest vines. Lastly, poison ivy flowers/fruits occur in axillary panicles - loose clusters containing 1-2 dozen flowers/fruits apiece - which emerge at the junctures of the leaves with their stems. Flowers are produced in the spring and early summer. They're quite small and inconspicuous. Fruits are also small -- each about the size of a BB. As summer turns to fall, the fruits mature from green to a dull, pale-yellow color. By late winter, those few which remain will have weathered to tan/brown.
In their poison ivy citation in American Wildlife & Plants, Martin et al mention that poison ivy fruits are consumed by birds "primarily in the winter, when other foods are scarce." That may be true in other parts of the U.S., but down here the annual avian "poison ivy festival" begins in earnest in September, when there is still an abundance of insects and other fruits present. Our recently published four-year Louisiana bird frugivory survey includes the following species observed consuming poison ivy fruits: Red-bellied Woodpecker, Yellow-bellied Sapsucker, Downy Woodpecker, Northern Flicker, Pileated Woodpecker, Eastern Phoebe, White-eyed Vireo, Blue-headed Vireo, Tufted Titmouse, Carolina Chickadee, Ruby-crowned Kinglet, Eastern Bluebird, Swainson's Thrush, Hermit Thrush, American Robin, Gray Catbird, Northern Mockingbird, Brown Thrasher. Cedar Waxwing, Yellow-rumped Warbler, White-throated Sparrow, Dark-eyed Junco, and Northern Cardinal. So, what about poison oak? Here in Louisiana, poison oak (Toxicodendron pubescens) is restricted to the pine/mixed pine forests north of I 10. How is it differentiated from poison ivy? That's a tough one. Since both species exhibit so much variability in leaflet shape, it would be difficult to point to one single character by which they might be distinguished. I will say, however, that the poison oak which I've personally examined (mainly in western Louisiana) did seem to possess more obviously bicolored foliage (dark-green above: light green below) which appeared to have more blunt tips to the leaves. Unfortunately - due mainly to geographical limitations - we failed to accumulate any observed interactions between birds and poison oak fruit during our statewide survey. I would guess, however, that usage would be on a similar order of magnitude as observed with T. radicans. Similarly, yet another closely related species, poison sumac (T. vernix, a small tree limited in distribution to pineland bog areas in Louisiana), sort of fell through the cracks in our survey, but again I'd guess the avian frugivory potential with this species to be high.
Though I usually end articles such as these with information on where and how to use the highlighted wild plant in garden settings, I wouldn't dare do so with this species! Keep in mind, however, that the Brits imported poison into their gardens long ago, owing primarily to the ornamental value of its magnificent fall foliage color. Good for them! Here in the southern U. S., poison ivy is way too rampant a grower to consider such usage -- Still, we should all allow poison ivy its place in uncultivated areas on our properties - especially those of us who (ahem) like birds.
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