Geographic variation in the plumage coloration of willow flycatchers Empidonax traillii

The ability to identify distinct taxonomic groups of birds (species, subspecies, geographic races) can advance ecological research efforts by determining connectivity between the non‐breeding and breeding grounds for migrant species, identifying the origin of migrants, and helping to refine boundaries between subspecies or geographic races. Multiple methods are available to identify taxonomic groups (e.g., morphology, genetics), and one that has played an important role for avian taxonomists over the years is plumage coloration. With the advent of electronic devices that can quickly and accurately quantify plumage coloration, the potential of using coloration as an identifier for distinct taxonomic groups, even when differences are subtle, becomes possible. In this study, we evaluated the degree to which plumage coloration differs among the four subspecies of the willow flycatcher Empidonax traillii, evaluated sources of variation, and considered the utility of plumage coloration to assign subspecies membership for individuals of unknown origin. We used a colorimeter to measure plumage coloration of 374 adult willow flycatchers from 29 locations across their breeding range in 2004 and 2005. We found strong statistical differences among the mean plumage coloration values of the four subspecies; however, while individuals tended to group around their respective subspecies’ mean color value, the dispersion of individuals around such means overlapped. Mean color values for each breeding site of the three western subspecies clustered together, but the eastern subspecies’ color values were dispersed among the other subspecies, rather than distinctly clustered. Additionally, sites along boundaries showed evidence of intergradation and intermediate coloration patterns. We evaluated the predictive power of colorimeter measurements on flycatchers by constructing a canonical discriminant model to predict subspecies origin of migrants passing through the southwestern U.S. Considering only western subspecies, we found that individuals can be assigned with reasonable certainty. Applying the model to migrants sampled along the Colorado River in Mexico and the U.S. suggests different migration patterns for the three western subspecies. We believe that the use of plumage coloration, as measured by electronic devices, can provide a powerful tool to look at ecological questions in a wide range of avian species.     

Divergent movement patterns of adult and juvenile ‘Akohekohe,an endangered Hawaiian Honeycreeper

The movement patterns of birds across a landscape are often highly variable and influenced by complex interactions between individuals and environments. Because periods of movement can be marked by high mortality, especially among juvenile birds, understanding these patterns may be vital for the conservation of many bird species. However, these patterns can be challenging to quantify. We used radio-telemetry to document the movement patterns of ‘Akohekohe (Palmeria dolei), an endangered Hawaiian Honeycreeper endemic to Maui Island, Hawai'i. This species is believed to be highly susceptible to mosquito-transmitted avian malaria (Plasmodium relictum) and only breeds in high-elevation wet forests on the windward side of east Maui (> 1715 m) that serve as mosquito-free refugia. Over a 2-yr period (2013–2014), we used radio-telemetry and resightings of color-banded birds to track the movements of juveniles (N = 11) and adults (N = 24) and quantified home ranges with minimum convex polygons (MCP) and 95% fixed kernels (KHR). Movement patterns and home range sizes of adult and juvenile ‘Akohekohe were significantly different, with adults having relatively small home ranges (0.57 ha, MCP; 1.09 ha, KHR) and juveniles moving greater distances and having larger home ranges (25.02 ha, MCP; 90.56 ha, KHR). Only juveniles moved into lower-elevation forests that can support mosquito populations, at least seasonally. The absence of adults in this transitional malaria zone suggests that adult ‘Akohekohe cannot maintain long-term home ranges in areas with an increased risk of malaria infection. In addition, the long-distance movements of juveniles during the post-fledging, pre-breeding period likely increases their risk of contracting avian malaria and could be a key factor limiting the population of this species.     

Phenotypic plasticity of the reproductive system of female Leptinotarsa undecimlineata

The effect of a non‐host plant, Solanum myriacanthum, on ovarian dynamics and longevity of Leptinotarsa undecimlineata (Stål) (Coleoptera: Chrysomelidae) was studied under laboratory conditions. Females reared on the natural host, S. lanceolatum, served as controls. Female beetles did not accumulate eggs on the non‐host. After continuous exposure to S. myriacanthum, the production of basal oocytes was diminished and oocytes were reabsorbed. Oocyte size, however, was not affected when compared to females fed with S. lanceolatum. In control females, the first mature eggs appeared at 34 days old. No eggs matured in females fed with the non‐host in the 54‐day duration of our experiment. Continuous exposure to the non‐host resulted in significantly less resorption of reproductive resources than a stress period of 20 days on the non‐host. Egg resorption was completely reversible after the preferred host was re‐offered for another 20 days. Further studies under field conditions will be necessary to understand why this Leptinotarsa species uses only one of two sympatric Solanum species.     

Responses to terrestrial nest predators by endemic and introduced Hawaiian birds

Birds free from nest predators for long periods may either lose the ability to recognize and respond to predators or retain antipredator responses if they are not too costly. How these alternate scenarios play out has rarely been investigated in an avian community whose members have different evolutionary histories. We presented models of two nest predators (rat and snake) and a negative control (tree branch) to birds on Hawai?i Island. Endemic Hawaiian birds evolved in the absence of terrestrial predators until rats were introduced approximately 1,000 years ago. Introduced birds evolved with diverse predator communities including mammals and snakes, but since their introduction onto the island approximately one century ago have been free from snake predation. We found that (a) endemic and introduced birds had higher agitation scores toward the rat model compared with the branch, and (b) none of the endemic birds reacted to the snake model, while one introduced bird, the Red‐billed Leiothrix (Leiothrix lutea), reacted as strongly to the snake as to the rat. Overall, endemic and introduced birds differ in their response to predators, but some endemic birds have the capacity to recognize and respond to introduced rats, and one introduced bird species retained recognition of snake predators from which they had been free for nearly a century, while another apparently lost that ability. Our results indicate that the retention or loss of predator recognition by introduced and endemic island birds is variable, shaped by each species' unique history, ecology, and the potential interplay of genetic drift, and that endemic Hawaiian birds could be especially vulnerable to introduced snake predators.     

Extracting useful data from imperfect monitoring schemes: endangered butterflies at San Bruno Mountain,San Mateo County,California (1982–2000) and implications for habitat management

Managers surveyed for sensitive butterfly species in the San Bruno Mountain Habitat Conservation Plan area between 1982 and 2000 using an opportunistic “wandering transect” method. To extract as much valuable information as possible from the data collected by this method we analyzed patterns of surveys and butterfly presence and absence within 250 m square cells gridded across the area within a Geographic Information System. While estimates of butterfly abundance were not possible, the data could be tested for trends in butterfly occupancy. For those cells surveyed during at least 10 years, no trends in the total number of occupied cells was evident for either Callippe silverspot or mission blue butterfly. There were cells, however, that showed positive or negative trends (P < 0.20) in occupancy for each species (Callippe silverspot: 14 positive, 15 negative, 6 cells occupied all years; mission blue butterfly: 40 positive, 40 negative, 2 cells occupied all years). We conclude that for the period 1982–2000 the population of each species was stable in overall total distribution, but indicate geographic areas of concern for each, specifically the edges of the northeast ridge for Callippe silverspot butterfly and the northwest of the study area for mission blue butterfly. Vegetation composition analysis using orthophotography with field corroboration indicates that those areas with declines in occupancy for these species experienced native coastal scrub succession and a corresponding loss in grassland butterfly habitat, while positive trending and stable cells had stable grassland proportions. Habitat managers at San Bruno Mountain should therefore incorporate programs for protecting grassland butterfly habitat not only from invasive weeds but also from succession to native coastal scrub. This approach illustrates the feasibility of using occupancy as an indicator to track butterfly status in a protected area even when suboptimal data collection methods are used, but the difficulties of using these data also reinforces the need for managers to devise monitoring schemes appropriate for their objectives before implementing them.