4.7 Reproduction and feeding behavior
Given the number of feeding visits to the Llano Grande Gumbo Limbo by
both male and female Scarlet-rumped Tanagers, I am certain they had a
nest nearby and were feeding the fruits to their young. I also once saw
either a female or young Scarlet-rumped Tanager sitting hidden
underneath a bush right next to this tree. [After reading Skutch’s
account of fledged Scarlet-rumped Tanager behavior, I now wonder if what
I saw was indeed their fledgling (Skutch 1980)]. This was also the
only Gumbo Limbo where I observed Scarlet-rumped Tanager. Scarlet-rumped
Tanagers are very common birds, so their absence in other trees
indicates Gumbo Limbo fruits are not a major food resource for them.
Their presence in only this tree is further indication that they were
feeding young. Either they took advantage of a convenient food source to
feed their chicks, or perhaps the high sugar and lipid-poor content of
Gumbo Limbo may have met the nutritional needs of its young, but not
have been needed by the adults.
McDiarmid et al. (1977) surmised that the arils of Huevos de
Caballo may not be a suitable food for young birds. The basis of their
assumption was that in only five of ninety-six observations of
Hoffmann’s Woodpeckers feeding their young had the young been fed the
arils of that fruit. Unlike theirs, my observations suggest that
the lipid-rich arils of Huevos de Caballo may be an important
nutritional need of several species of newly-hatched birds, specifically
Hoffmann’s Woodpecker, Yellow-green Vireo, and Rufous-naped
Wren.
I made fifty observations of feeding done by Hoffmann’s Woodpecker with
forty-four done at Willy’s Huevos de Caballo . As previously
noted, there was at least one nest hole of Hoffmann’s Woodpecker close
by. I observed both males and females fly in, grab one of the “fruits”
(arils) and immediately fly off. On 11 April 2021, adults flew in and
grabbed fruit eight times in an hour, and on 15 April 2021, they did
this nine times within a half-hour. Several of those times I followed
the bird to its nest hole and observed the young being fed, and I assume
it was also being fed on those occasions when I did not follow the bird.
I also saw fifty-one instances of feeding being done by Yellow-green
Vireos, with forty done in Willy’s Huevos de Caballo . From 11
April to 15 April I observed 23 different feedings in this tree. Birds
arrived to feed both singly and in pairs, and like the Hoffmann’s
Woodpecker, the birds flew in and out grabbing fruits constantly.
Although I did not see a Yellow-green Vireo nest near this tree, given
this concentration of feeding behavior, I suspect there was a nest
nearby.
Finally, I observed twenty-nine similar instances of feeding by
Rufous-naped Wren in Willy’s Huevos de Caballo. As Rufous-naped
Wren is a very common species that nests in gardens, it is likely there
were many nests and young nearby. Again, the frantic feeding behavior of
the adults was similar to that of Hoffmann’s Woodpeckers, which led me
to believe they too were feeding young.
What might account for the differences between my observations and those
made by McDiarmid, especially with respect to Hoffmann’s Woodpeckers? My
observations of Hoffmann’s Woodpecker feeding on Willy’s Huevos de
Caballo were made over a period of over a month (25 March to 29 April)
with the greatest number of feedings from 11-15 April. In contrast, Mc
Diarmid’s observations at the Hoffmann’s Woodpeckers’ nest site were
done on one day, 25 April. Could it be that the young they observed
being fed were at a stage where insect protein was a more important food
source for them? It may be that earlier in their development the young
are more in need of lipid-rich nutrients. Alternatively, perhaps there
were insufficient quantities of insects during the earlier period of my
observations, and the Hoffmann’s Woodpecker were substituting a readily
available food resource.
In conclusion both Gumbo Limbo and Huevos de Caballo are
important food resources in the neotropics for both frugivorous and
insectivorous species of birds. Gumbo Limbo fruits are high in sugar
content, and consumed by many normally insectivorous birds and migrants,
and as my 2022 study shows, the tree is especially important as an
energy source toward the end of the dry season when other trees are not
in fruit. In contrast, Huevos de Caballo provides fruits high in
lipids which many larger and mostly resident birds consume. Both trees
also seem to be important sources of nutrition for young birds during
their development and help to maintain bird diversity in populated
areas. The continued use of Gumbo Limbo as living fences and cultivation
of Huevos de Caballo should both be encouraged to maintain bird
diversity in areas of human habitation.