Blakeman: Is the nest bigger?

The nest --Photo taken on December 9, 2006 [two weeks ago]

The nest -- May 2005 [more than 18 months earlier]


I sent a note to John Blakeman asking him to comment, based on photographs available on Lincoln's PaleMale.com website, whether the nest looks noticeably more substantial this year than last. After all there was a big flurry of nest-building activity in December and January 2006. Here is his answer:


About the depth of the nest.

From the photo, it just doesn't look like the nest itself is much thicker or deeper than before -- which is your concern, too.


As I mentioned at the very beginning, it appears that red-tails bring sticks to the nest and tuck them in only as long as the entire mass of twigs and sticks are loose. Once they consolidate into a larger, cohesive mass, the birds stop concerning themselves with the nest's size. When it feels solid, they perceive the main nest structure to be complete. After that, they tend to proper lining of the nest, bringing in leaves, grass, and other loose materials to form the egg-supporting bowl.


If the nest feels solid, there is no impelling need for the 5th Ave pair to do much nest tending. As either of the birds walk around or sit in the nest, everything feels solid and secure. The pigeon prongs artificially knit the whole mass of sticks together.


But you've seen them bringing sticks to the site, so how does that fit in with my contention that they aren't really concerned about making the nest deeper? The important factor is what do they do here in December and January with the brought-in sticks before nest refurbishing becomes a powerful behavior just before eggs are laid in March. Bringing sticks to the nest can be either useful, or merely incidental to the birds' experiences and presently minor breeding behaviors. To be of any effect, the sticks have to be not only brought to the nest area, but they must be deliberately tucked into the central nest structure (not the metal support).


The birds can incidentally bring sticks to the nest and more or less leave them perched loosely on the top or edges of the nest proper. A good winter wind will blow these off and be of no use. Useful sticks are carefully tucked in sideways between other sticks and locked into the structure. Those sticks won't be lost to a wind gust up there. But they will contribute to a deeper nest.


So nest watchers need to see what the hawks are doing with the sticks once they are brought to the nest. Are they being ritually dropped and allowed to lay free (and useless) along the edges, or are they being taken into the bill and tucked sideways down into the existing central pile of sticks?


That will tell if the nest is going get thicker this season. If it does, we will have the best chance of resumed reproduction. If not, things may continue as they have for two consecutive seasons.

And it's appropriate that you've mentioned this just at the winter solstice period. By mid January, the birds will notice that the sun is rising earlier, and setting later. More importantly, there will be a few more minutes of daylight each day, as the winter progresses. We groundling mammals concern ourselves mostly with winter temperatures. Red-tails have remarkably insulating feathers. (Do we realize how cold we'd be drifting through 0-degree F winds at 40+ mph?) For the hawks, it's not the temperatures that control much of anything. For them, it's lengthening daylight periods, which initiates a cascade of hormones that prompt all of the breeding behaviors.


It's understood that even the loss of daylength (reduced "photoperiod") which happens in autumn, especially in November and December, can prompt a modicum of breeding or nesting behavior. That's what's been prompting the sticks retrievals to the nest so far. As the photoperiod begins to lengthen in January, the hormone prompts will be increase significantly and by early March will be the overwhelming behavioral drivers for both birds.


So the 2007 breeding season has actually begun, albeit so modestly or ritualistically just yet. Nest watchers should be attentive in recording what happens to the brought-in sticks. Are they dropped onto the nest (not effective), or are they actually tucked into its structure?


--John A. Blakeman

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