Tuesday, April 28, 2009


The result of all of that “love in the air” (see blog posting from February 25, 2009) is chicks which have hatched and are growing fast! I was able to catch a glimpse of these approximately 3-week old red-tailed hawk chicks in their nest on April 22. This same nest produced two chicks in 2006, likely from the same pair of hawks that are there now, as they can use the same nest for several years.

When I arrived, the mother was sitting on the nest, but after a while she flew off. A few moments later, two fuzzy white heads popped up! Then, they started pecking at each other, fighting like typical siblings. This photo is of the chicks in mid-fight. The mother was likely going off to hunt or retrieving prey from the father – either way, she will bring the prey (such as rodents, small mammals, even snakes) back to the nest and rip off small pieces to feed to the chicks. They will likely begin to leave the nest in about one month, after which they will continue to improve their flying and hunting skills by learning from their parents. At about 10 weeks old they should be completely independent from their parents. Check back soon, as we may be having a raptor expert come out and “band” the chicks (place small metal bracelets around their legs) so that their dispersal can be tracked over time as part of a regional study on raptor movements. Stay tuned!

Friday, April 24, 2009

An Endangered Visitor

While many people have heard of our resident threatened species, the coastal California gnatcatcher, we have an endangered species that is a seasonal visitor as well – the least bell’s vireo. The least bell's vireo is migratory, so it spends the winter in Baja Mexico, but comes up north into coastal southern California to breed in the spring and summer. It has been reported as breeding in the past at the nearby Whittier Narrows.

Larry Schmahl of the Whittier Audubon Chapter reported hearing one singing in Sycamore Canyon near the trailhead on April 9, 2009; I went out and also heard and saw an individual (possibly two!) on April 16th, and I heard and saw one again just this morning. The habitat in this location is perfect for the least bell’s vireo, as they prefer dense willow riparian habitat, including associated plants such as mulefat; however, they need some structural complexity in the habitat (i.e. multiple layers), so they often nest in early successional (newer) habitats including recently restored areas. Since the riparian habitat at the Sycamore Canyon trailhead was restored within the past few years, the vireo may stick around and nest this year. Although a single least bell’s vireo was observed at this location in 2005, it did not stay to breed; however, the site may now have developed the level of habitat structure that it needs to breed – we’ll be keeping an eye, or rather an ear, out throughout the rest of the spring and summer. If the vireo continues to be seen or heard through June or July it is likely nesting in the area, and will remain until it migrates back down to Baja in August or September.

Although the least bell’s vireo has experienced population increases recently, it is still subject to threats such as habitat loss from the removal of riparian vegetation, as well as from nest parasitism from brown-headed cowbirds. These cowbirds are known to lay their own eggs in the nests of other species, including the least bell’s vireo, which result in much larger and earlier-hatching chicks that compete with the vireo chicks for food – cowbird chicks can even toss vireo eggs out of the nest before they hatch! We’ll be keeping an eye out for them as well.

Photo credits: Upper - U.S.G.S ; Lower - USFWS, Photo by Po-Hon Liu.

Wednesday, April 15, 2009

The snake days of spring

OK – I know I already talked a little about snakes in my last blog, but given the frequency of snake observations over the last few weeks I think they deserve further attention. In fact, just yesterday I saw 3 different snakes in the Preserve in less than 3 hours! Snakes are now emerging from their winter hibernation sites and can often be found basking in the sun, stretched out in open areas. They are especially common laying across roads and trails where they can absorb the maximum amount of sun and heat from the asphalt or dirt; so keep your eyes peeled on the trail ahead – the “stick” you think you are seeing might actually be a snake! They are best spotted in the morning when they are trying to warm up for the day, since they usually retreat to vegetation or sheltered areas during the peak heat of the day in the afternoon.

I observed this young Southern Pacific rattlesnake (only about 1.5 feet) in the middle of the asphalt road in the core habitat area. Because I was driving along the road and did not want to crush it, I nudged it with a stick to make it move – it rattled a bit at me, annoyed that I was making it leave the warmth of the road, and then it reluctantly slithered off into the brush. Although this young rattler was old enough to have actual “rattles” at the end of its tail, very young rattlers only have a single “button” and cannot yet make the rattling sound. Notice the stripe or mask along its eyes and the striped skin pattern near the end of its tail, as opposed to the diamond or square patterning on the rest of its body. Rattlesnakes find their prey using heat-sensing pits on the sides of their head. Also, these snakes bear live young in the late summer, as opposed to many other snakes which lay eggs.

I observed this large San Diego gopher snake sunning itself on the road/trail right near the Arroyo Pescadero amphitheater. These snakes are very commonly observed and are not venomous, but they can sometimes inflate their head and shake the end of their tail to imitate a rattlesnake when they are threatened. They kill their prey by constricting them – coiling their body around the animal and squeezing it. The patterning on gopher snakes is highly variable, but they are generally the largest and longest of the snakes you will commonly see on the trail.

This California striped racer was seen near the Colima Road tunnel along the Arroyo San Miguel trail – I saw it chasing a small rodent across the road. This snake often holds its upper body off the ground (as shown in the photo) to help them to see and find prey with their highly acute eyesight. These snakes are also not venomous. Notice the long slender black body with the yellow stripes along its entire length – these stripes are on both sides of the body.

Although it is sometimes frightening to stumble upon a snake while hiking, it is important to respect their place in our ecosystem, as they help to keep rodent populations under control. Their beauty and diversity is one of the many things to appreciate and enjoy in the hills!