Today's Discoveries

It turns out I never made it to Sand Prairie yesterday as planned.  Instead I visited the conservation area today after my summer class.  My plans were to record the weight of the eggs in nest #5 and to survey the vegetation immediately surrounding the nest.

I was delighted to find a bird incubating nest #5, indicating that it is still in use.  There were still only two eggs.  Measurements were taken for the eggs and the vegetation was sampled in a square meter plot surrounding the nest.  I wanted to make sure I did both at one time to minimize the number of nest disturbances.  To my surprise it took me awhile to relocate the nest, but while I searched two adult birds flew in rough circles above me.  They called sporadically but did not land, at least not near me.  I assumed they were the pair that had constructed nest #5, but since I later startled the female off the nest, this must have been a different pair.  My adviser, Dr. Eddleman, suggested the possibility of polygyny, where multiple females nest within the territory of a single male bird.  I will have to look into this further.

I also spent a good while observing birds around the dunes.  This is where four out of the first five nests were constructed and where I have seen the vast majority of birds.  Not far from nest #1 is a persimmon that is a favored perch for a particular pair of sparrows, most likely the ones who built the nest.  I observed a bird with an insect in its beak and waited patiently for it to fly to its nest.  It did not move but was soon joined by a second bird with an empty beak.  The second bird eventually flew to the west, while the bird with the insect flew a good distance south.  Both seemed to leave what I thought was their territory.

Several minutes later I located a different bird only a few meters in front me with a green caterpillar in its beak.  The bird remained motionless for a while before crouching down and walking stealthily to a concealed nest.  This nest was located beneath a plant that still needs to be identified and contained 4 young birds.  Because I had already disturbed the nest I decided to take the weight, length, and tarsal measurements of 2 of the young.  One of the birds weighed 6.1 grams, while the the other weighed only 3.1 grams.  Based on Baepler's (1968) weight measurements, I would estimate these birds to be between 2-3 days old.  Since Baepler's study indicates an increase of roughly 2-3 grams per day, the smaller bird may well have hatched one day later than the heavier one.  The larger bird had a total length of 43mm, while the smaller bird was 36mm in length.  Tarsi length was 13.5mm and 11mm, respectively.

I was able to locate the vicinity of another nest but was never able to find the nest itself.  Both parents returned to the area with insects in their beaks but neither entered a nest.  Instead they either remained still or crept slowly among the bunches of grass.  Both this pair and the pairs before indicate a high degree of caution among lark sparrows when it comes to concealing their nest.

Because both of these nests are located among the dunes, my hypothesis is that they are re-nesting attempts by the same pairs that previously experienced nest predation.  In order to lessen the risk of predation I do not intend on returning to these nests for at least 2-3 days.