Season Wrap-up: Another Banner year for our Naturelines.

Welcome to the internet's gathering place for Purple Martin enthusiasts
Post Reply
Scully
Posts: 2008
Joined: Mon Jan 26, 2004 5:35 pm
Location: Texas/San Antonio

The end-of-season silence has descended upon our colony. I had expected nesting activity through the first half of July but two late clutches failed to hatch and a late brood of three has perished, judging by the remains all as undersized twenty-day olds.

For the past three years we have been offering various combinations of different gourds for purposes of comparison. In 2003 we offered Naturelines and Carrols, In 2004 we offered Naturelines, Supergourds and Big Bos, all SREH. The results obtained each year have been interesting, but our sample sizes were too small to draw definite, statistically sound conclusions.

This year we offered 12 Naturelines, 10 Supergourds, 9 Big Bos, 8 Bo Villas and 2 Bo gourds, again all SREH. Our sample sizes are still small, but the consistent solid performance of our Naturelines over all three years is becoming noticeable.

Season Summary:

12 NATURELINES: All gourds occupied. 52 nestlings fledged from twelve gourds (4.3 fledged/nest)
10 SUPERGOURDS: Nine gourds occuppied. 37 nestlings fledged from nine gourds (4.1 fledged/nest)
9 BIG BOS: Eight gourds occupied. One failed clutch. One dead brood. 23 nestlings fledged from six gourds (3.8 fledged/nest)
8 BO VILLAS: Five gourds occupied. One failed clutch. 14 nestlings fledged from four gourds (3.5 fledged/nest)
2 BOS: Both gourds occupied, one a second time after an early death of the first brood. 9 nestlings fledged from two gourds (4.5 fledged/nest)


One should alway be wary when viewing statistics, note that the apparent standout performance of the little Bo gourds was based on just two gourds. The little Bos may be great, and our one gourd offered last year fledged five young, but three gourds is simply too few to draw conclusions from.

Three years in row however, the total of 37 Naturelines we have offered over those years have suffered only 4 vacancies and produced nestlings at a rate as good as or better than competing gourd designs. Much of this productivity seems to be a function of an early start of the nesting season. Our martins seem to love our Naturelines and, on average, occupy them at an earlier date. Because of this, fewer Naturelines on average end up hosting the less-productive SY pairs.

One notable disadvantage of our Naturelines has been a vulnerability to starlings, even with crescent SREH's. All our Naturelines have been equipped with inside/outside cling rods below the crescent to aid the martins. Next year we will offer our Naturelines without the outside rod to see how this affects martin preference and starling entry.

On balance, this has proved at best a moderately succesful year for our martins. Thirty-three pairs of martins fledged a total of 135 nestlings for an overall productivity rate of 4.1 fledged/pair.

However, if we include those two failed clutches and one lost brood, all late enough in the season to preclude a second nesting attempt, then thirty-six pairs of martins fledged those 135 young for an overal success rate of 3.8 fledged/pair.

All in all, given the normal annual mortality of martins, we about broke even population-wise.

Mike Scully
Sandy - NC
Posts: 617
Joined: Tue Nov 11, 2003 6:40 pm
Location: Rocky Mount, NC

Mike, how would you say the WDC entrances did? Do you think they helped? Did you have any breached by starlings?
Scully
Posts: 2008
Joined: Mon Jan 26, 2004 5:35 pm
Location: Texas/San Antonio

Sandy... we have been impressed with the WDC entrances. The martins learn them quickly and slip in and out with impressive ease, possibly important if it should give them an extra second to evade a hawk attack.

None of our WDC entrances were invaded by starlings, although by random chance eight of the ten were hung on the "low risk" pole, one that has proven to be, probably because of location, less attractive to starlings than the other poles. The remaining two were hung on "high risk" poles, and a crescent Natureline on one of these poles did get invaded.

Next year I will be sure to hang a bunch of the WDC Supergourds in "high risk" locations :lol:

One possible WDC entrance design flaw in the context of the way we hang our gourds was this: Our gourds are suspended 18" away from the pole on 3/4" allthread rod, usually with the entrance facing outwards. Given the weight of a Supergourd, these gourds when so hung often droop on the rod, assuming a slightly entrance-down position.

We installed the WDC tube entrances flush with the outside, such that the 3" tunnel projected inside of the gourd. Some martin pairs filled up the nest cavity to the level of the entrance tube.

The result was that, in a few gourds, the entrance to the nest was effectively a relatively smooth, downsloping tunnel level with the surface of the nest. The danger of fallouts seemed obvious, although only one was known to occur among the nine WDC Supergourds we had occupied.

Regards,
Mike Scully
Post Reply