Longer days at hummingbird feeders in Las Vegas NV – changes in the bird population

                As the year moves towards spring the length of daylight gradually increases. It is this change in the hours of light that is a primary factor in the changes of the seasons. That is why even here in Las Vegas NV, where winters temperatures stay relatively mild, deciduous trees lose their leaves in the fall. Birds leave for their wintering grounds long before their food supply runs low. Both happen because of the lessening in the hours of daylight available to them.

                Shorter hours of sunshine mean less energy for the trees to use for photosynthesis. Less daylight means less time for the birds to forage for food. Trees must store food in their roots and rest for the winter. Birds fly south where the days are longer and the weather warmer.

This photo was taken Nov 10, 2013. The lowest temperature at that time was 42 degrees, but the days were shortening.

                In the spring the reverse happens. More hours of daylight bring a northward movement of birds and the return of leaves on trees. I have seen this happening all around me since the middle of February. Even though the weather warmed to well above normal in January spring changes did not start until the days became visibly longer.

This photo was taken March 14, 2014. Temperatures had been in the 70s for several weeks. Day finally got long enough for the leaves to emerge.

                Early in the morning, long before sunup, I hear flocks of killdeer calling as they fly over the valley on their way to parts north. I see small flocks of Mourning doves resting briefly in my yard as they move through on their northward journey. The numbers of White-crowned sparrows visiting my feeder decrease as spring comes closer.  Those that remain are rapidly putting on their summer dress.

Molting White-crowned Sparrow just getting his white and black head. Also some of his wing feathers are just growing in.

Inca Dove finally visits my yard instead of just calling in the distance.

I was sure the Mourning Dove would chase it away, but they fed peacefully together.

                The world is coming alive with the calls of birds. House finches, Mocking birds and Mourning doves all begin to practice their songs, getting ready for breeding season. Inca doves call in the distance.

                Yet one bird has reversed the process. I have heard a Costa’s hummingbird since the middle of February. One day in the middle of the month my house was surrounded all day by the whistling call of the Costa’s. The next day I didn’t hear a single whistle and haven’t ever since.

                I tend not to notice absence as quickly as I do presence. I did note that the north-side feeder didn’t need refilling as quickly as it had. At first I thought maybe there was something wrong with the feeder, so I gave it an extra cleaning and refilled it. Even then it just didn’t go down as fast. Then I noticed that the Anna’s feeding at the west-side feeder weren’t being chased away from the feeder, although they were still leery of settling, but that could be explained by the passing of finches on the way to the seed sock.

Anna's female hummingbird coming in to feed. Photo filtered to show details.

                It finally dawned on me. The Costa’s hummingbird was gone. Certainly it hadn’t gone north yet, spring isn’t far enough advanced for that.  Then I remembered, it was June 12 last year when the Costa’s made its first showing at my feeder. So where was it all spring?

                According to the bird guides, the Costa’s hummingbird prefers to spend spring in the desert. It only comes to town when the weather turns hot and the desert is no longer blooming. That is why I didn’t see him at my feeder until the middle of June.

                Okay, then why did they leave after spending all winter at my feeders? What could the desert offer that they couldn’t get in town?

                I finally thought to look at the app on my iPad, The Ultimate Southwest Desert Field Guide by the Audubon Society.  There was the answer under flowers that bloom in February. The red siren that lured the Costa’s away from my red feeders was Justicia californica. It goes by the common names of Mexican honeysuckle or Chuparosa, which is the colloquial name for hummingbird in Spanish. Another common name, this one says it all, is the hummingbird bush.

                This bush blooms from February through June. Its range matches the wintering range of the Costa’s hummingbird, except for that little piece called Las Vegas NV, where hummingbird feeders and introduced plants abound in the winter, but even that is not enough to keep the Costa’s from the desert in spring.

                As the other birds are slowly making their way northward, the Costa’s abruptly left for the southern deserts. The longer days and bright red blossoms lured it away, until June. Then it will be back at my feeder here in Las Vegas NV.