Marin County Parks Experiences Spring Fever
By David Herlocker, Naturalist
Are you having trouble focusing on your income tax forms with this beautiful weather pressing in around you? Don’t feel too guilty, it’s probably natural. In spite of the fact that we celebrate romance and pair formation in February (on Valentine’s Day of course); right now is the time when nature seems to be totally focused on the mating game.
Walking the trails of Marin County Parks open space preserves, the casual observer can’t help but notice that the rocks and logs along the trail are now adorned with the bodies of sunning Western Fence Lizards (they are those scaly looking gray lizards that we called “blue bellies” as kids). If you stop for a moment to watch them, you might see them chasing each other and occasionally performing their territorial displays, which look like push-ups to us. These push-ups and mechanical head-bobs are their way to display the bright blue patches on their throats and bellies. Displays of this sort are intended to impress unmated females and to intimidate rival males. If you see two lizards that appear to be fighting you might have to look a bit closer, they may actually be mating. After mating, a female might continue to spend time near her mate. He will benefit her by chasing off bothersome amorous males, leaving her free to feast on the flies and other insects which land within this prime feeding territory.
Are you noticing that you are awakened each morning to the melodies of singing birds? Many of these love songs are an indication that our songbirds are beginning their annual mating rituals. Many of the birds that breed here are really only temporary residents; they spend the larger portion of the year in the tropics. During their brief visit to our region they totally focus on procreation. As spring approaches, they begin to move north, stimulated by hormonal urges that drive them to seek out optimal breeding habitat. Most birds usually return to the same area where they were born, males tend to arrive a week or so ahead of the females. Males use their songs and (in many species) bright colors to establish territories. When the females finally appear, these songs and visual displays attract them to the most impressive males. If a female likes the location (in terms of food availability, and suitable nesting location) she will set up housekeeping with the resident male. For most of our typical land birds, nest construction will take a week. This is followed directly by a week of egg laying punctuated by quick (but frequent) bouts of copulation. Once the clutch of eggs is complete, the pair might share two weeks of incubation, two weeks of feeding the growing nestlings, and then another couple of weeks hanging around the area as a family before they split up and head south again at the end of summer. Enjoy these sweet voices of spring; all too soon they will grow silent as the brief breeding frenzy plays itself out around us.