Predators

Introduction

The original title of this Chapter was going to simply be – Predators, however some predators are just that – predators, while some pests are just that – pests, but there are others which are, to varying degrees, both predator and pest and thus the title was expanded to embrace Predators and Other Pests.

The first problem I encountered in preparing this article was one of attempting to classify our principal predators and other pests by dividing them into categories which share common characteristics of one sort or another.  Initially, I thought I would then sub-divide them into discrete groups by size, or family, genus and species and then whether they are diurnal or nocturnal, but it soon became apparent that using this approach was both too difficult for me with so many variables, and also perhaps too scientific and/or complicated for a BACK TO BASICS series.

Size varied from microscopic (as with bacteria), to minute (mites and lice), to small (ants) and so on, all the way through to our larger animals and reptiles (some of which can exceed 2 metres in length).  I have chosen to omit from this Chapter all of the pests smaller than say, a cockroach, preferring that they be discussed in some detail in a future Chapter titled – Hygiene and Care.

A further attempt at sub-division as being either –

  • diurnal (primarily active by day, sleeping at night)
  • nocturnal (primarily active at night, sleeping by day)

was also not entirely satisfactory because some, cats for example, can be a problem during the day and/or night.

Whilst, in the broadest sense, predators and other pests are fairly widely distributed across the whole of Australia, certain species can be both prolific and widely distributed, others however, much less common, or mostly confined to specific geographic locations. This Chapter only attempts to address the issues on the broader geographic scale and not on a location specific basis, although some references are made to South-East Queensland.

Finally, this Chapter aims to supplement the information provided in other Chapters in this BACK TO BASICS series where there is potential for overlap, or duplication of some of the information, e.g. –

  • Aviary Design
  • Aviary Construction
  • Hygiene and Care

The Main Culprits

This segment attempts to identify and address the problems that the main culprits represent in aviculture, whilst the whole range of predators and other pests also encompasses a number of others which are not nearly as serious, or as frequently, a problem.

The presence of a single predator or pest in an aviary is undesirable, but an infestation of cockroaches, geckos, mice or rats can have devastating effects, and also prove extremely difficult to eradicate – two of the main reasons being the abundance of supply of both a wide variety of food and hiding places.  The on-going presence of food, which is often quite palatable and sometimes high in protein, makes the task of enticing pests into conventional forms of traps using other food sources as “bait” to attract them, extremely difficult, but nevertheless, should be tried and persisted with.

Cockroaches can often be caught in “traps” comprising a glass jar having Vaseline smeared around the top inside rim of the jar and food such as ripe banana, honey or peanut spread placed in the bottom.  Geckos may also be expected to be caught in this same trap.

An aviary with 6 x 6mm wire and the minimum of gap widths in its construction, might just keep adult sized geckos out, but not small juvenile ones . . . and it doesn’t take too long before small geckos grow into full-sized adult ones, once inside the aviary.  Gecko activity during the cover of darkness can be very disturbing to both roosting and nesting birds alike, and it is generally accepted that large geckos will feed on newly hatched chicks of small birds such as finches.  Those aviaries which provide some form of night lighting only exacerbate the problem of geckos, in that these lights attract moths and other flying insects, which in turn, also attract geckos in larger numbers.

A “gecko-specific” type of trap has been devised which consists of a small purpose-made timber box (or coffin!) with a small hole in each end.  Inside, on the bottom of the box is “sticky board” which ensures that the intruder “keeps very still” until it can be disposed of.  (Q.F.S. intends to include a separate article about this gecko trap in a future edition of Finch News.)

The conventional “snap-shut” form of mouse trap poses an additional problem of needing to be housed in a receptacle with a hole large enough to allow the mouse to enter, but small enough to prevent any birds from entering.  Obviously this approach is impractical in the case of rats, as any opening which allows a rat to enter would also allow many aviary size birds to also enter.

Forms of traps which allow mice or rats to enter into, but not exit from, are available, but as mentioned above presents a difficulty in providing a food source which would prove irresistible to the rat or mouse, given the range of food already available in the aviary.  Cheese, pumpkin seeds or peanut spread are worth trying in an attempt to trap mice, but left-over dinner bones with a little meat, gristle or fat might just be enticing enough to trap a rat.

The use of poisonous baits to deal with a mouse or rat problem introduces additional problems of its own.  If they are used to treat mice or rats which are known to be present on the outside of the aviary, then consideration needs to be given to the potential access to the baits by the “unintended’  e.g. children, domestic pets, other wildlife, free range poultry, etc.  If baits are used inside an aviary, then great care will need to be taken to ensure that the birds in the aviary cannot also access them.

The rat has a well-deserved reputation for being cunning (which gave rise to the old saying “as cunning as a s**t-house rat”).  One such rat showed considerable cunning in devising a rather lengthy and convoluted route along roof beams and rafters to where some over-lapping woven bird wire lining the underside of the roof framing could be prised apart, thus providing an access and exit point to the aviary proper, and also to the nesting boxes mounted some little distance below the roof.

After blocking the entrance hole of the Gouldian nesting box with its torso, this rat then feasted on an adult Gouldian and its young before retracing its route to escape, intending to return again whenever it needed another feed . . . or so it thought!  Now the ever-vigilant owner of the aviaries was on his daily rounds, and of course saw the total devastation inside this particular Gouldian nest box.  After searching for some considerable time, the owner finally established the means by which the rat had gained entry for his nocturnal feast.

Using bird wire, a rather crudely formed enclosure was fabricated which encapsulated the whole nest box (preventing any birds from gaining entry) but which still provided access for the rat from the roof framing above.  Inside the nest box a conventional “snap-shut” rat trap was set.  Sure enough, next morning the lifeless tail of a rat protruding from the entrance to the nest box told a very satisfying story in itself.

As with a rat, a snake, which by some means or other has gained entry to an aviary, can also cause considerable loss of stock if left undetected for a period of time. There have been occasions when, with only enough time to attend to the essential feeding and watering before heading off to work, an aviculturist has not been able to observe the slowly diminishing number of birds in his collection . . . until it is too late!  With an abundance of hiding/resting places amongst brush or in nesting boxes, such a snake will happily live in “snake heaven” . . . at least until it is caught and released back into its natural environment. (It is recommended that this release be some considerable distance away, otherwise you should expect a second encounter of the same snake kind.)

On more than one occasion when checking Gouldian nest boxes, I have been able to detect the presence of a snake inside the box even before lifting the lid, purely by the extra weight of the box.

Whilst the particular species of the most frequently offending snake may well vary on a location by location basis, anecdotally it would seem that the non-venomous pythons (or more commonly called “carpet snakes”) are most often the main culprits in South-East Queensland.

All of the preceding predators and other pests are at their damaging worst after having gained entry to the aviary, but there are still others which may never, or at least rarely, ever gained access to the aviary itself.  After all, if there is an opening that something bigger than all of the preceding predators and other pests can get in through, then obviously, the aviary birds could also escape through.

Now it is a sad fact in the life of an aviculturist that several of the most annoying and frustrating of our predators and other pests are other avian species.  Some, such as native Australian noisy minors seem to be present in ever-increasing numbers, at least in South-East Queensland, whilst the introduced species of Indian minor is reported to be the bigger problem in the southern States.  These “minors”, both of which are fiercely territorial, have driven away many other more desirable native species out of “their” habitat and seem quite intent on “harassing” captive aviary birds.  They operate in tight family groups, both during this harassment or when confronted by an intruder into their territory, and can readily be observed calling for reinforcements to ward off such an intruder.

Another problem avian species is the butcher bird, which, as well as harassing in smaller groups of two or three, are more intent on predation than the minors and have caused the demise of many a caged or aviary bird, without ever having gained entry to the cage or aviary.

I suspect that the percentage of aviculturists who are also cat lovers is a very small minority.  Whilst keeping cats “out” of the aviary is not a matter of real concern, keeping them “off” the aviary often is, and particularly so during the night in the case of homeless and/or feral cats.  Keeping cats off the entire property is the most satisfactory solution and having an active and alert one of “man’s best friend” can be invaluable in helping to achieve this outcome.

Many Local Councils have regulations requiring domestic cats to be housed at night and not left to roam freely about.  Aviculturists greatly appreciate compliance with such regulations by many responsible catowners.

Protecting Our Birds, Our Investment and Our Sanity

Many old sayings embody elements of either truth and/or wisdom, and so it is with the saying  –  “Prevention is better than cure.”

Commitment and attention to detail, with regard to –

  • hygiene,
  • chemical barriers, and/or
  • physical barriers

as the means by which predators and other pests can be prevented from gaining access to our aviaries, cannot be over-emphasised.

In general terms, the primary defence against the smaller size groups of our pests, is by means of good hygiene practices and/or chemical treatments or barriers. The most effective means of providing, and then maintaining, both good hygiene and chemical treatments or barriers will be the subject of a future Chapter in this BACK TO BASICS series, titled “HYGIENE & CARE”.

Physical barriers are treated in more detail below and also in other Chapters in this series.

Q.F.S. members in South-East Queensland are very fortunate in having ready access to our monthly meetings where we generally hear informative (and sometimes entertaining) lectures/presentations on a wide variety of avicultural topics.  One such presentation, both informative and entertaining, was given just recently at our October meeting by a young woman from the Management Committee.  She confessed that, as a beginner aviculturist, she thought the principal, and even the sole purpose of the construction of an aviary, was to keep the birds “IN” . . . BIG MISTAKE !   As a wiser and more experienced aviculturist, she has now come to the realisation that a very significant proportion of the cost, and of attention to the construction detail of an aviary, is dedicated to keeping predators and other pests “OUT”.

 Unlike parrots, which are generally much larger, heavier and stronger than finches, and with an entirely different beak configuration, and which also seem physically and genetically predisposed to chewing, tearing, stripping and gnawing away at most things within their aviary, finches could be kept in a cardboard box with fiberglass fly-wire, without much risk of them escaping. However, it is the risk of predators and other pests violating such flimsy security measures that gives us a strong motivation to devise methods of  keeping them out.

Keeping the Bastards OUT 

Quite obviously, the No.1 means of protecting our birds against direct attack is to keep  predators and other pests out of our aviaries in the first place. Although it might initially appear obvious that this suggests a solution to the problem, it is only a partial solution and does not, in itself, guarantee complete protection, as attacks from the outside of an aviary also represent a very real pest and risk problem, albeit with a somewhat reduced ‘predator’ mortality rate on our birds.

As mentioned previously, a significant number of caged and aviary birds have been killed by predators operating from the outside of the cage or aviary.

Nevertheless, it is the introduction of physical barriers that affords the most effective “lines of defence” protection against those predators and other pests, from mouse size upwards.

This first line of defence begins below ground level with the construction of a barrier (most commonly referred to as a rat wall) to rodents which are capable of burrowing to a depth of some 300-400mm below surrounding ground level.  The rat wall should therefore be extended to a minimum depth of 600mm to provide satisfactory protection against these “burrowers”.  (Refer also to Chapters 1. and 2. – “Aviary Design” and “Aviary Construction” respectively, for further information on the use and construction of rat walls.)

The second line of defence requires meticulous attention to detail in avoiding ‘gaps’ greater than say 3-4mm, in any part of the aviary’s construction, including for example, the fitting tolerances around door openings or feeding access hatches. Gaps of 5mm or wider only invites and ensures entry into your aviary of mice and small snakes. Whilst it may seem obvious that “the wider the gap, the larger the size of the potential predator”, one cannot also discount the apparent ability of rodents, and snakes in particular, to seemingly “partially flatten” themselves and to squeeze through gaps that you would not have thought possible     . . . at least until experience teaches you otherwise.

The management of ‘gap widths’ will, in many cases, be on-going, as settlement, or other movement of the natural ground, together with thermal expansion and/or contraction of the aviary materials themselves, (as well as shrinkage or decay in the case of timber framing), can cause gaps to appear, which otherwise did not pre-exist.

The third line of defence requires a vertical surface which prevents, or at least severely inhibits, the scaling (or climbing up) ability of pests attempting to negotiate the external walls of the aviary which incorporate bird wire, and which would otherwise provide access for them to the aviary wire, or other vulnerable aspects of the aviary construction. This is often best provided by the use of metal sheeting which, with the readily-available colorbond finish, also offers an aesthetically acceptable appearance.  An inverted ‘u’ shaped metal capping which protrudes outwards from the face of the vertical metal sheeting also further inhibits access to the aviary wire, as well as offering protection from the sharp top edge of the metal sheets.

The fourth line of defence is the wire itself, which should not be larger than 6mm x 6mm if you are making a serious attempt at keep everything from small mouse size upwards, out of the aviary.  Wire of this size also significantly inhibits the depth of penetration into the aviary of the beaks of such predators as butcher birds. Existing aviaries using 12mm x 12mm wire sometimes require the use of a second or double layer of wire spaced about 50-60mm off the face of the original wire, as a means of limiting the reach and access of the beaks of butcher birds (and some other birds) to the aviary birds.

In certain circumstances which require it, a fifth line of defence can be achieved with the introduction of electrically charged wires (high voltage but low amperage), similar to electric fences used to control horses and cattle. These are usually mounted off the external extremities of the aviary by insulators and are generally only needed to be brought into use at night, although they are also useful against domestic cats and predator birds in situations where aviary complexes are unable to be kept under sufficient observation during prolonged periods of daylight hours.

When predator activity occurs at night, as is often the case, the risk of injury to the birds, together with potential loss of clutches of incubating eggs or chicks, is significantly greater than if the activity occurred during daylight hours. Cats, snakes, possums, rats and nocturnal predatory birds all cause a great deal of stress, potential injury and even death when they harass our birds at night, even though they remain confined to the outside of the aviaries.

Some physical barriers can also be inadvertently voided. Whilst foliage from shrubs and trees, together with man-made structures which surround, or are in close proximity to our aviaries, can enhance the aesthetic aspect of an aviary complex, it can also lead to the circumventing of some of the physical barriers we have put in place as part of our defence strategies. Snakes and rats, in particular, are well-known users of such means of gaining access to, and sometimes entry to an aviary, having thus found a way around a whole range of otherwise effective barriers.

In conclusion, there can be a tendency for beginner aviculturists to cut a few corners when it comes to taking preventative measures in keeping predators and other pests out of their first aviaries. This can be attributable to either an understandable keen-ness to complete their aviary and begin stocking it with their finches of choice, or a lack of knowledge of the very real risks and dangers they are subjecting their birds to.  However, experience is a great teacher and the disappointment that comes with those first harsh lessons of birds lost and damage done, should bring to mind the sombre words from a pop song of a few years ago “good advice . . .  that I just didn’t take”  –  “Prevention is better than cure”.

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