There has been much consternation about what has been happening at this nest over the last few days. The new male, now named Beau (earlier V3), began a solid bond with the continuing female, Gabrielle (Gabby) last spring. She laid her first egg this season on 12/19/23. But Beau has not shown any interest in the egg, and on the evening of 12/22/23 he buried it.  Here is my current take on the situation.

I’ve seen eagle adults bury eggs several times over the 13 years I’ve been watching nest cams. The most recent example is at the Kisatchie E-3 nest in Louisiana, where the resident female (Andria) died on 12/9/23 and a new female appeared within hours. She covered the 2 eggs several times for a few days, but the male (Alex) has always uncovered them and is still incubating. Perhaps SWFL followers will remember a somewhat different situation in 2016, when M15 kept covering Harriet’s first egg in the days after it was laid, even though he wasn’t an intruder and had raised 2 fledglings with her the year before. He may have been shielding it from daytime heat while neither he nor Harriet was incubating. Harriet dug up that egg and laid another, although only 1 hatched. I’ve observed other instances as well, and I’ve also seen intruders destroy eggs or hatchlings (MD Blackwater in 2011, CA Redding in 2013, BC White Rock in 2013, WI E4K in 2016, OH Sandy Ridge in 2017, PA Hanover in 2018, FL NEFL in 2018, MN DNR in 2018).

So what is happening with V3/Beau? Let’s think through things, starting with whether or not Gabby’s egg was fertilized. Maybe, maybe not, there is no way to know. If it wasn’t, then the contents of the shell is just Gabby’s gamete, some yolk, and some albumen. If it was fertilized, then does Beau “knows” that the egg is “his” or, alternatively, does he suspect that it isn’t “his”? Well, birds don’t read biology books. They don’t know what “sperm” is. They don’t know what “fertilization” is. All they “know” is that they are stimulated to proceed through specific behaviors throughout the year, which lead to certain results – like the production of an egg. The question really doesn’t make sense for birds.

Why won’t he incubate? As I’ve explained before, because of the challenges by other males in the days leading up to Gabby’s egg, V3 was in fight mode. During the crucial pre-egg period, his reproductive hormones may have been keeping up with hers, but the challenges by other males threw his schedule off. Hormones from the Adrenal Glands (Corticosterone, Epinephrine, Norepinephrine) ramped up quickly. These hormones have a chemical make-up that enables them to have an almost immediate effect, unlike the reproductive hormones, which act more slowly. They stimulate various bodily systems (respiration, heart rate and blood flow, increased glucose and lipid production, suspension of digestion) to enable the eagle to respond to challenges quickly. These hormones also dampen secretion of the reproductive hormones. Meanwhile, Gabby’s system continued on its reproductive path, and she laid an egg on 12/19/23. Under typical circumstances, her reproductive hormones would remain active so that ovulation of a second egg could occur within a few hours after the first egg was laid. We don’t know yet whether that happened with Gabby, but if it did, that egg should have been laid yesterday evening. Or, her system may have perceived V3’s disinterest in her egg, and the resulting stress (exhaustion, hunger, etc.) may have induced her ovary to delay ovulation for a day. Or the ovary could have deposited the next mature ovum into her abdominal cavity instead into the oviduct, and it would thus not be fertilized and would be absorbed into the surrounding tissues.

In both females and males the brooding hormone, prolactin, begins a significant rise in secretion just before ovulation. For Gabby’s first egg, ovulation occurred three days before she laid it, on 12/16/23, and by the time she laid it, even while her reproduction hormones were still active in anticipation of the next ovulation, she also had ample prolactin in her system. Not so with Beau. The last recorded visit by another male was on 12/13/23. Adrenal hormones dampened the reproduction hormones during the stressful days, but as the adrenal hormones declined, his reproductive hormones and behaviors slowly began to emerge again as he perceived the situation to be calming down. But by that time his hormonal balance was hopelessly out of sync with Gabby’s.

Why did he bury the egg? I don’t think anyone can know the answer to that for certain. But 12/19/23 marked a huge change in Beau’s experience. Throughout that day he and Gabby were adding materials to the nest, chatting with each other, and flying and perching together, and he “practice” incubated in the nest cup for a while. At about 6 pm, everything turned upside down for him. Suddenly Gabby stopped perching and flying with him and instead spent hour after hour in the nest cup. If this is Beau’s first attempt at breeding, as many people believe, he may never have seen an egg before. He may have had no idea what it was or where it came from. And unless he had raised a clutch of eaglets in prior years, he would have had no clue that this thing might contain a tiny collection of cells that would steadily grow until one day that hard white shell would break apart and out of it would emerge a living, breathing, cheeping, hungry chick. All he knew was that Gabby’s behavior was bewildering, and that somehow it was connected with that large white thing that she kept spending all her time on top of, ignoring him except to yell at him. The times we saw him nosing around in the fluff around the egg, from the morning after it appeared until he finally and definitively buried it on 12/22/23, I think he was simply trying to restore things back the way they were. I don’t think he was trying to harm the egg, there is no reason to believe that he thought it might contain anything alive or threatening or edible. I think he was just trying to make it go away.

If Gabby continues to incubate, even if much less than before, prolactin is still flowing in her system. If she eventually decides to stop incubating altogether, her prolactin will recede and her reproduction hormones could stimulate another ovulation for a second clutch.

ADDENDUM: Gabby laid her second egg on 12/23/23 at 17:15. So she did delay ovulation for a day. Time will tell whether Beau’s hormones have caught up to hers — or hers have backed up to his — and he is able to incubate. And whether this egg is fertilized.