David H. Ellis

POST-RELEASE SURVIVAL OF HAND-REARED AND PARENT-REARED MISSISSIPPI SANDHILL CRANES

Abstract The Mississippi Sandhill Crane (Grus canadensis pulla) reintroduction program is the largest crane reintroduction effort in the world. Here we report on a 4-year experiment in which we compared post-release survival rates of 56 hand-reared and 76 parent-reared Mississippi Sandhill Cranes. First-year survival was 80%. Surprisingly, hand-reared cranes survived better than parent-reared birds, and the highest survival rates were for hand-reared juveniles released in mixed cohorts with parent-reared birds. Mixing improved survival most for parent-reared birds released with hand-reared birds. These results demonstrate that hand-rearing can produce birds which survive at least as well as parent-reared birds and that improved survival results from mixing hand-reared and parent-reared birds.

Motorized Migrations: the Future or Mere Fantasy?

Abstract In 15 experiments from 1993 to 2002, we led cranes, geese, and swans on their first southward migration with either ultralight aircraft or vehicles on the ground. These experiments reveal that large birds can be readily trained to follow, and most will return north (and south) in subsequent migrations unassisted. These techniques can be used to teach birds new (or forgotten) migration paths. Although we are constantly improving our training techniques, we now have an operational program that can be broadly applied to those species whose juveniles learn migration routes from their parents.

Summer diet of the peregrine falcon in faunistically rich and poor zones of Arizona analyzed with capture-recapture modeling

Abstract We collected prey remains from 25 Peregrine Falcon (Falco peregrinus) territories across Arizona from 1977 to 1988 yielding 58 eyrie-years of data. Along with 793 individual birds (107 species and six additional genera), we found seven mammals and nine insects. In addition, two nestling peregrines were consumed. We found a larger dependence upon White-throated Swifts (Aeronautes saxatalis) and birds on migration in northern Arizona, while in southeastern and central Arizona average prey mass was greater and columbiforms formed the largest dietary component. In northern, central, and southeastern Arizona, 74, 66, and 56 avian prey taxa, respectively, were recorded. We used capture-recapture modeling to estimate totals of 111 ± 9.5, 113 ± 10.5, and 86 ± 7.9 (SE) avian taxa taken in these same three areas. These values are counterintuitive inasmuch as the southeast has the richest avifauna. For the entire study area, 156 ± 9.3 avian taxa were estimated to be taken by peregrines. Dieta Estival de Falco peregrinus en Arizona Comparando Zonas Ricas y Pobres en Avifauna Mediante un Modelo de Captura-Recaptura Resumen. Desde 1977 a 1988 colectamos restos de presas en 58 nidos de Falco peregrinus a través de Arizona. Conjuntamente con 793 aves individuales (107 especies y seis géneros adicionales), encontramos siete mamíferos y nueve insectos. Además, fueron consumidos dos pichones de Falco peregrinus. En la zona norte encontramos una mayor dependencia sobre Aeronautes saxatalis y aves en migración, mientras que en las zonas sureste y central la masa promedio de presa fue más grande y los columbiformes constituyeron el componente principal de la dieta de Falco peregrinus. En las zonas norte, central y sureste se registraron 74, 66 y 56 taxa de aves presa, respectivamente. Para estimar el número total de taxa capturados por Falco peregrinus usamos un modelo de captura-recaptura. Los valores calculados fueron 111 ± 9.5, 113 ± 10.5 y 86 ± 7.9 (EE) taxa para las zonas norte, central y sureste, respectivamente. Estos valores no reflejan los que esperábamos, ya que la zona sureste tuvo una avifauna más rica. Se estimó que 156 ± 9.3 taxa fueron capturados por Falco peregrinus en la totalidad del área de estudio.

Golden Eagle predation on experimental Sandhill and Whooping Cranes

During experiments to lead cranes on migration behind motorized craft in the western United States, our cranes experienced 15 attacks (4 fatal) by Golden Eagles. We believe many more attacks would have occurred (and more would have been fatal) with-out human intervention. We recognize eagle predation as an important risk to cranes especially during migration.

Thinking about Feathers: Adaptations of Golden Eagle Rectrices

ABSTRACT “Happy is the man whose lot it is to know The secrets of the earth.” Euripides Abstract The striking black and white plumage of the juvenile Golden Eagle (Aquila chrysaetos) provides an excellent opportunity to examine the possible selective forces influencing the strategic placement of dark pigment in birds. The conflict between opposing selective pressures (first, toward large white patches, which may allay aggression in adults, and second, toward dark plumage to promote camouflage and limit solar and abrasive wear) provides the stage whereon are revealed a score of pigmentation traits of potential adaptive value. The general pigmentation trend is for zones that are more exposed to the sun to be darker than elsewhere. More specifically: (1) for rectrices and remiges, outer webs are darker than inner; (2) for those few feathers (e.g., central rectrices, some scapulars, and some tertials), where both inner and outer webs are heavily and nearly equally solar exposed, pigmentation is supplied similarly on both webs; (3) outermost primaries and rectrices are darkest of all and are structurally similar; (4) for central rectrices, subject to high levels of abrasion with substrate, the tip is paler (resultant flexibility may limit breakage); and (5) pigment is heavier along or on the rachis than on the webs. Many of the traits listed above for the Golden Eagle are also found in other families of birds. Traits of the tail common to many species were a terminal pale tip, a subterminal dark band, rachis darker than vane, and outer webs darker than inner for both remiges and rectrices. The most widespread traits likely have adaptive value.

Cheaper by the Dozen: Bald Eagles Capture Many Fingerlings with Each Attempt at Fish Boils in Coastal British Columbia

Bald Eagles (Haliaeetus leucocephalus) normally capture sizable fish, one at a time. We here describe feeding bouts off the northern Queen Charlotte Islands, Canada (54u159N, 133u049W), wherein Bald Eagles congregated at fish boils (sometimes termed bait balls and pods) and grasped many small fish at each attempt (Fig. 1). Mass capture seems to be unreported in the extensive Bald Eagle literature (Lincer et al. 1979, Stalmaster 1987, Buehler 2000). Our observations suggested that this behavior is typical under some circumstances. The most completely documented feeding bout we observed occurred on 20 May 2009 between 15:20 H and 15:38 H. At the onset, about 10 Bald Eagles were seen circling and diving at a very small spot on the ocean surface ca. 1 km from shore. We hurried to the eagle concentration zone in an inflatable boat and began counting birds and photographing foraging. At maximum, 21 Bald Eagles (of which only two were not white-headed) were in the swarm. The eagles flew around the bait ball in ca. 75-mdiameter circles with an eagle diving at the fish boil every 3–5 sec. Some eagles were only about 3 m apart when they hit the water. All swoops were into the wind. Most were low, linear passes, but some involved a twisting maneuver before a short, steep stoop. The eagles grabbed at the water surface with both feet. After the grab, an eagle typically swung to one side, rose to 9–15 m, began circling and drifting downwind, and commenced feeding on the fingerlings. During feeding, scales and whole fish were dropped into the water as the eagles attempted to feed without losing their grip. Some photographs showed an eagle with 10 or more fish (Fig. 1). The bait ball was a ca. 3-m-diameter mass of 10–15-cm long fish. The size of the fish was estimated from photographs of fish in gull bills (up to five fish at a time in the bills of some Glaucous-winged Gulls [Larus glaucescens]) and eagle talons. As such, they were probably second-year and older Pacific sand lances (Ammodytes hexapterus; identification by T. Reimchen; aging from Vermeer et al. 1987). Because Bald Eagles typically quarrel over food, a remarkable feature of this and subsequent feeding bouts was that the eagles did not pursue one another to steal food. The benefits of forcing another eagle to drop (and scatter) tiny fish would, of course, be minimal. Our focus on the capture site (about 15 m from our boat) precluded us from following any one eagle, but our impression was that successful eagles (and all attempts appeared to be successful) consumed their prey on the wing, returned to the bait ball, and swooped in again. When eagles were present, Glaucous-winged Gulls (ca. 50 present) remained on the periphery of the activity, but during brief lulls in the eagle strikes, some gulls darted in to gather fish at the bait ball. After the bait ball was sufficiently diminished, the eagles quickly stopped circling and flew away toward shore. The gulls then quickly reassembled to gather remnants of the school. Throughout the foraging bout, Rhinoceros Auklets (Cerorhinca monocerata; ca. 200–300 present) dived and surfaced about 5–10 m from the bait ball; it appeared that they kept the fish massed at the surface but consumed them beneath the water; only once was an auklet noted at the surface with a fish. Other seabirds aggregated at the fish boil included one Herring Gull (L. argentatus), one immature Black-legged Kittiwake (Rissa tridactyla), ca. five Common Murres (Uria aalge), and two cormorants (probably Phalacrocorax pelagicus). Because we saw no salmon (Salmo sp.) or other large predatory fish, and because of the diving activities of the Rhinoceros Auklets, we concluded that it was the auklets that maintained the bait ball near the surface, as is consistent with auklet feeding activity described by others (Grover and Olla 1983). Another closely observed feeding bout occurred on 2 June between 16:00 H and 16:05 H. After drifting with the tide in an inflatable boat for ca. 2 hr, we saw an eagle energetically flapping out to sea. We followed to an assembly point again ca. 1 km offshore. Although many seabirds also gathered this time, only about 14 eagles (including three birds without white heads) participated. Eagles swooped at the fish only about four times and without apparent success (i.e., no feeding observed), then scattered for shore. We then motored very close to the pod and saw that it consisted of much smaller fish (ca. 7–10 cm in length and therefore probably first-year sand lances) than seen on 20 May. Also, the fish were not in a globular cluster but in a ca. 2-m-long, tightly packed, serpentine line ca. 15 cm wide and moving very slowly as the fish crowded together at the surface. With the gulls at the surface and the auklets diving (and presumably attacking from below), this swarm of fish was quickly consumed. It

On the uniqueness of color patterns in raptor feathers

Abstract For this study, I compared sequentially molted feathers for a few captive raptors from year to year and symmetrically matched feathers (left/right pairs) for many raptors to see if color patterns of sequential feather pairs were identical or if symmetrical pairs were mirror-image identical. Feather pairs were found to be identical only when without color pattern (e.g., the all-white rectrices of Bald Eagles [Haliaeetus leucocephalus]). Complex patterns were not closely matched, but some simple patterns were sometimes closely matched, although not identical. Previous claims that complex color patterns in feather pairs are fingerprint-identical (and therefore that molted feathers from wild raptors can be used to identify breeding adults from year to year with certainty) were found to be untrue: each feather is unique. Although it is unwise to be certain of bird of origin using normal feathers, abnormal feathers can often be so used.