Reprinted from: Update 10(4)
Purple Martin Conservation Association
|A female martin peers from a Troyer Horizontal Gourd equipped with a clip-on porch. While some martins at the PMCA's site nested in unmodified Troyer Gourds, the addition of porches seemed to encourage them to explore these new gourds and entrance designs.||At the Purple Martin Conservation Association's research site in Edinboro, PA, martins nested in natural and plastic gourds modified with crescent and Excluder plates, both with and without porches. Since Excluders were developed for use with porches, it's probably best to use porches with all Excluder entrances.|
One of the reasons we enjoy martins is because of the fact that they return faithfully to our backyards each season. They are old friends, back from far away places; they reassure us that all is still well with the world. Their rooms are waiting; perhaps it is reassuring to them as well, and they eagerly move back in.
During this past breeding season, some landlords complained that the new housing they had purchased and erected at their established colony sites was not well-used by martins, and was therefore somehow flawed or undesirable to martins. Namely, we received complaints about two new plastic gourds with crescent entrance holes: the crescent SuperGourd and the Troyer Horizontal Gourd (both first introduced to the market in 2001). And we also heard from landlords who were experiencing anxiety about how quickly their birds were or were not adapting to new Excluder and crescent entrances they'd added to houses. I listened to quite a few people who felt they had purchased inferior housing because the martins had not used them, or because they had very low occupancy the first season. While no housing is without flaws, I feel it is erroneous to judge the quality of the housing based on first or even second year occupancy rates. New housing is often the last to be occupied (as is housing with crescent entrances placed right next to housing with round entrances).
Martins are well-known for their loyalty to established housing. How many times have we heard the story of newly-arriving martins perched on, or fluttering near, the empty pole or closed housing they nested in the year before, while they waited for their tardy landlord to raise or open their house for the new season? And how many times have we heard landlords bemoan the fact that they have offered their martins newly-built and superior housing, only to have them snub these new digs and return to their old decrepit house? And of course we all know the tale of the frustrated "would-be" landlord, who offers brand new and superior housing only a short distance from an established, but neglected site, only to have the martins move back into the slum housing, which is literally falling apart and filled with House Sparrows!
Should it be any surprise, then, that martins are often slow to inhabit the new housing we erect in our backyards? The advice the PMCA has always given to landlords wanting to transition their martins into new housing is to erect the new housing in close proximity to the old, and leave it there for at least one breeding season, giving at least a few pairs the chance to breed successfully in the new housing, before removing the old. In most cases, only a few pairs of martins will use the new housing the first season, regardless of what type of housing it is. Martins are creatures of habit and tradition, and are usually reluctant to embrace new housing (just as they are often reluctant to establish new breeding sites).
The same reasoning and strategy applies to someone wishing to expand their colony site. New housing is often slow to be colonized, regardless of whether it is superior to the old. For example, at one of the colony sites monitored by the PMCA in 1999, the landlord erected a Deluxe Gourd Rack with 12 round-holed, plastic SuperGourds next to an existing rack of eight round-holed natural gourds. The established rack had almost 100% occupancy. Not a single pair of martins nested in the new rack that first season, but two years later, the new rack experienced 75% occupancy (8 of 12 SuperGourds used).
One way to speed up the use of newly-introduced housing might be to mix it in with the established housing. For example, if your colony is established in a gourd rack with 12 natural gourds with starling-resistant entrance holes (SREH), and you are adding a gourd rack with 12 plastic gourds with SREH, rather than putting them all on a new rack in a new part of your yard, use a combination of natural and plastic gourds on both racks. This will help the martins become familiar with the new housing more quickly.
I believe that martins will, to some extent, accept and move into almost any type of new housing at an established site, provided they are exposed to it for a sufficient period of time, and assuming it is properly placed and managed. Unless there is a housing shortage, a great demand for housing, or some other unusual circumstance, it is unrealistic to expect more than token occupancy of newly-erected housing the first season, and it is unfair to judge the quality or acceptability of new housing based on first-year occupancy rates.
Follow-up on SREHs
Landlords continued to report success with crescent and Excluder SREHs this season. Martins at the PMCA's main research site nested successfully in a variety of housing-types, including plastic and natural gourds with crescent SREHs (both SuperGourds and Troyer Horizontal Gourds) and Excluder plastic adapter plates, both porched and unporched. The martins definitely seemed to prefer the porched gourds, most likely because it was easier to negotiate the entrance. I believe that porches are a good thing for plastic gourds with SREHs, and will help to increase occupancy by making them easier to enter and exit. Landlords with porchless SREH gourds should consider increasing traction below the entrance hole, both inside and out. One way to do this is to use a dremel tool to create a series of closely placed horizontal grooves. Traction is also a concern for aluminum houses with SREHs. I recommend using grit paint or waterproof friction tape to increase traction on the floor under the entrance holes (both inside and out) on aluminum houses with SREH. This past season, I found two adult female martins that appeared to have gotten stuck; one was entering a crescent SREH in a Trio Castle; one was exiting an Excluder SREH in a Trio castle. There were many successful nesting attempts in both types of entrances, however.
At Pymatuning State Park, in Linesville, Pennsylvania, a newly-erected gourd rack with 12 unmodified, porchless crescent SREH SuperGourds, achieved 75% occupancy in it's first season (2001). Similarly, Warren Wochek of Naples, Florida, erected a PMCA Deluxe Gourd Rack with 12 unmodified crescent SuperGourds and had nine nests the first year.
Tony Frederickson, in Seguin, Texas, gave the Excluders he tested on Lonestar houses high marks: "At the beginning of this (2001) martin season, I installed 14 Excluder adapters on a new 14 compartment martin house. I immediately witnessed starlings attempt and fail, numerous times, to gain entry into the 12" deep cavities. Throughout the season, more of the same - but never did a single starling violate the Excluder. How did the Purple Martins do with the new SREH? Fantastic! In all, there were eight martin nesting attempts - all successful! The eight martin pairs laid 41 eggs, 38 of which hatched. Every single nestling (38) fledged."
Changing to SREHs is recommended and will not cause martins to abandon a site, but I caution against making drastic changes to small, single-structure colony sites. For example, changing both the entrance hole-type and the material composition (from natural to plastic gourds, or from wooden to metal houses, etc.) might be considered a radical change by the martins and could cause site abandonment.
Keep in mind that every colony site is somewhat unique. Some are large, some small. Some are long-established; some recently. Some are situated in ideal habitat and some in marginal or poor habitat. As a general rule, landlords with large, well-established colony sites in areas of martin abundance can get away with manipulating the housing at their colony sites much more radically than can landlords with very small sites in marginal habitat. Whatever you choose to do, there will always be risks, and there are never guarantees.
Consider this hypothetical account: A landlord tried for ten years to establish a colony site. He was very vigilant in controlling starlings. After ten years, he finally attracted one breeding pair, but decided not to switch from round to SREH the following season, because he did not want to risk losing his only pair. This pair returned the following season, to the landlord's delight, and built their nest. The female laid a full clutch of eggs and shortly thereafter was killed by a renegade starling that had escaped the trap and gun. The male abandoned the site, and the landlord abandoned the hobby, forever. While this landlord was correct in not making any radical changes (since he had such a small colony site), he lost his only breeding pair by trying to "play it safe." He could have converted to an SREH after the female had laid her clutch of eggs. He could have added an adjustable starling-resistant entrance. At the least, he could have converted some round entrances to SREHs between seasons; the pair may have chosen one to nest in. Any of these options might have preserved his colony site.
For additional information about Starling-Resistant Entrance Holes (SREHs), see articles in Update 3(4), pp. 8-9; Update 5(3), p. 10; Update 8(4), pp.10-13; Update 9(4), pp. 10-11; Update 10(1), pp. 8-10; and Update 10(2), pp. 2-5.
Copyright 1998 by Purple Martin Conservation Association. All Rights Reserved.
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