Tuesday, July 29, 2014

Red-tailed Hawk

At the Mission Nature Park and Bike Trail on 23 February, when we spied this raptor, we thought we found our quarry, a Hook-billed Kite. It seemed russet-breasted and slender. But closer examination of my photos proved this to be a western Red-tailed Hawk adult, intermediate between light and dark morphs. I had never before observed this plumage.
This Red-tailed Hawk race breeds across most of western Canada. Some individuals are dark, others pale, and some intermediate, with still others intermediate between these three morphs. Why do Red-tailed Hawks come in different color phases? One hypothesis is that prey species learn to identify what a Red-tailed Hawk should appear. This learning makes the prey vulnerable when a different morph appears. If the odd morph becomes more common, due to its hunting success, then the prey learns the new plumage patterns, and another morph will be favored.

Monday, July 28, 2014

Greater Roadrunner

When we searched for Hook-billed Kites along the Mission Nature Park and Bike Trail on 23 February, we did not see the raptor, but did watch a Greater Roadrunner hunt along the trail. Roadrunners are curious, terrestrial cuckoos. They feed on “snakes, lizards, spiders, scorpions, insects, birds, rodents, and bats” and, in times of food shortages, its own young (Hughes 2011). Roadrunners are monogamous and maintain long-term pair bonds. Both sexes incubate their eggs and feed their young. Roadrunners have been increasing in numbers and moving north and east from their traditional southwestern range, which includes Texas and Louisiana.

Sunday, July 27, 2014

Neotropic Cormorant

This Neotropic Cormorant is identified by its relatively small size and by the white line behind its lower mandible. Erika and I found this cormorant, on 23 February, a day we devoted to unsuccessfully searching for two rare birds, the Hook-billed Kite and Fulvous Whistling-Duck. We discovered this bird at Lake Edinburg, only to discover that the lake is closed on Sundays, making the whistling-duck search impossible.

For reasons unknown, Neotropic Cormorants greatly declined during the 1960s in the United States, but have resurged since that decade. Recently the species has been even reported in the Dakotas and elsewhere in the Upper Midwest, as well as Canada and Pennsylvania. Normally Neotropic Cormorants breed from south Texas through much of Latin America. This species is relatively tolerant of human activities and can survive diverse habitats and climates (Telfair and Morrison 2006).

Friday, July 25, 2014

Roseate Skimmer

This gray-sided dragonfly turns out to be a female Roseate Skimmer. We also found this species species in 2012 when we last visited Estero Llano Grande State Park in south Texas. This pose is typical for the species, which perch on twigs with their abdomens below the horizontal (Paulson).This author describes Roseate Skimmer copulation as aerial, and lasting only some 10 seconds. Females either deposit their eggs directly into the water or splash water onto adjacent banks.

Visiting this park later in the spring or summer would probably yield a great number of dragonflies. The park consists of a network of wetlands, ideal for both insects and birds.

Thursday, July 24, 2014

Least Grebe

In 2012 during our last visit to Texas, we saw many Least Grebes. Last February we only saw this one, at the Estero Llano Grande State Park. Texas had suffered from several years of drought, which probably adversely affected grebe habitat.  Least Grebes have high reproductive rates and generalized feeding habits, so are able to recover from adverse weather trends. Although not migratory, this species is able to fly considerable distances in search of appropriate habitat (Storer 2011).

Tuesday, July 22, 2014

Buff-bellied Hummingbird

Buff-bellied Hummingbirds breed along the coast of the Gulf of Mexico, north to southern Texas and south to Belize and Guatemala. In Texas this species is common from March to August, becoming rare in the fall and winter. Like many hummingbirds, undoubtedly some post-breeding Buff-bellies migrate south. But, uniquely, a few disperse into the southeastern United States. Records exist from most southeastern states, from Arkansas to Florida and North Carolina. At least in Louisiana, winter records may be on the increase (Chavex-Ramirez and Moreno-Valdez 1999, Rubythroat.org).

Erika and I were delighted to photograph this Buff-bellied Hummingbird at the Estero Llano Grande State Park. Hummingbirds were not abundant during February, but patience in front of one the the park hummingbird feeders paid off. We listed this species during our March 2011 visit to Santa Ana National Wildlife Refuge, but then we only saw one uncooperative individual.

Monday, July 21, 2014

Ruby-throated Hummingbird

Also at the hummingbird feeder at the Estero Llano Grande State Park, perched a bird I could not initially identify.  Turns out to be a Ruby-throated Hummingbird. This was late February, when, typically, Ruby-throats molt their body feathers. This molt begins towards the bird’s bottom end and proceeds towards the head. Thus this bird is molting in its bright throat feathers. Weidensaul et al. (2013) also note that, especially in the winter, males occasionally have orangey throats. The cause of this orange color is not well understood.

This spring in Northfield, Erika and I enjoyed seeing many Ruby-throated Hummingbirds in more typical plumage, such as the bird below.

Sunday, July 20, 2014

Black-chinned Hummingbird

Black-chinned Hummingbirds breed across much of western North America and central Mexico. In the United States, they winter north only into southeastern Texas—that is, until the 1980s, when they began to be reported across much of the southeastern United States. This change is not well understood—where they always there, but undetected? Have they moved in because of habitat change? Is it the result of more people keeping winter hummingbird feeders?

Erika and I photographed this male Black-chinned Hummingbird Hummingbird at the Estero Llano Grande State Park. The bird fed at a hummingbird feeder at the park headquarters, making visits about every 20 minutes. Fortunately a bench was strategically placed nearby.

Saturday, July 19, 2014

White-faced Ibis

Erika and I added the White-faced Ibis to our February trip list at the Estero Llano Grande State Park in south Texas. I have previously posted a note on how to differentiate between White-faced and Glossy ibis. The White-faced Ibis is the more likely species in most of Texas. The species breeds in the western United States and winters in Mexico, western Louisiana, and eastern Texas. Also note the red facial skin on this ibis. This area is dark or blue in Glossy Ibis.

The two ibis have interbred in captivity, but are not known to do so in the wild. Thus, for the time being anyway, they are considered to be distinct species (Ryder and Manry 1994).

Thursday, July 17, 2014

White Ibis

White Ibis inhabit coastal areas of the southeastern United States, Mexico and Central and South America. The birds inhabit both estuarine and freshwater swamps. These ibis shift their roosting and colony sites in response to water availability and to concentrations of crustaceans and small fish. Curiously young birds do not survive when fed crustaceans from salty water. Therefore, White Ibis depend on freshwater breeding sites (Heath et al. 2009). 

This aversion to brackish water crustaceans probably does not affect these White Ibis that Erika and I found on 22 February 2014 at Estero Llano Grande State Park. I have previously posted notes on this species.