Sentences with phrase «predation rates»

Data on predation rates by pet cats in Canada would also be very helpful.»

We excluded studies from outside temperate regions and those with predation rate estimates based on fewer than 10 cats, < 1 month of sampling, or on cats that were experimentally manipulated (for example, by fitting them with bells or behaviour altering bibs).

More recently, Dauphiné and Cooper use the inflated predation rate suggested by Lepczyk et al. (along with rates proposed by other researchers) to arrive at their «billion birds» figure.

Our results suggest that nest predation rates in Rusty Blackbirds may be driven more by ecological processes such as masting (years of higher - than - normal cone production), rather than timber harvesting, which we found not to be a strong predictor of nest survival.

After excluding studies that did not meet a priori inclusion criteria designed to increase the accuracy of our analysis, we developed probability distributions of predation rates on birds and mammals.

In addition, overlap in use of nest sites with coexisting species may increase nest predation rates [21].

Thus, predation rates measured through prey returns may represent one half to less than one third of what pet cats actually kill...» [7]

The authors conclude that surveying predation rates with questionnaires alone isn't sufficient since the self - reported numbers aren't always accurate.

Based on these numbers, then, we can estimate the yearly predation rate of House sparrows at ST5277 to be roughly 125 — well short of the minimum proposed by Baker et al. (and just a quarter of their intermediate rate).

Indeed, such a question will invariably overestimate the number of «outdoor cats» — which in turn overestimates predation rates.

The two studies can not be compared directly for a number of reasons, but by way of comparison, the average predation rate used by Lepczyk et al. is approximately 31 birds / cat for the 22 - week breeding season.

We combined predation rate distributions with literature - derived probability distributions for US cat population sizes, and we also accounted for the proportion of owned cats allowed outdoors, the proportion of owned and un-owned cats that hunt, and imperfect detection of owned cats» prey items.

«If you have a species whose predation rate depends on that size, you can have strong trophic effects without even thinking about abundance changes.»

«The disparity between human and animal predation rates is a useful way of illustrating how ecologically out - of - whack many exploitation rates and management policies are.»

Hunters and non-hunters: skewed predation rate by domestic cats in a rural village.

This Australian study looked at predation rates among owned cats over a two - year period when wearing the Birdbesafe collar cover.

This is a critical point when it comes to connecting predation rates (from cats or any other predator) to population impacts.

In other words, no difference between predation rates predicted by actual hunting observation and those predicted by way of prey returned home.

What Lepczyk et al. have done serves just one purpose: to inflate apparent predation rates.

In it, she touches on all the usual talking points (e.g., cats are non-native, exaggerated predation rates, etc.), and portrays her trapping as a civic duty — done in the best interest not only of the community, but also of the cats.

Barratt has shown that the actual predation rate, at this level, is less than half the rate predicted by cat owners.

Impact To arrive at their figure of «532 million birds killed annually by outdoor cats,» Lebbin et al. multiply «the most conservative predation rate (5.6 birds per cats per year) by the most conservative estimate of outdoor and feral cats in the U.S. (95 million).»

Cats and Birds As evidence of the «variable predation rates by cats,» [2] The ABC Guide refers to just four studies.

Studies were only included if: (1) they clearly reported cat ranging behaviour (that is, a description of whether cats were owned or un-owned and whether they were outdoor cats or indoor - outdoor cats), and (2) the group of cats investigated fit exclusively into one of the two groups we defined above (that is, we excluded studies that lumped owned and un-owned cats in a single predation rate estimate).

Mean predation rates within each square each season were multiplied by cat density to estimate the total number killed, and summed across seasons to estimate the number killed annually.

Our finding that un-owned cat population size and predation rate explained the greatest variation in mortality estimates reflects the current lack of knowledge about un-owned cats.

DNA analysis of swabs taken from radio - collars and carcasses of these woylies indicated that predation by cats (Felis catus) caused most mortalities (65 %) and was three times the fox predation rate (21 %).

Aggregate predation rates, for example, fail to differentiate across vastly different habitats (e.g., islands, forests, coastlines, etc.), species (e.g., songbirds, seabirds, etc.), conditions (e.g., sick and healthy, young and old, etc.), and levels of vulnerability (e.g., ground - nesting and cavity - nesting species, rare and common species, etc.).

Magic Multipliers For Dauphine, Lepczyk's estimated 52 birds / cat / year predation rate simply isn't enough.

For years now, ABC has been promoting erroneous and misleading information (e.g., baseless feral cat population numbers, exaggerated / erroneous predation rates, etc.) in their tireless effort to vilify free - roaming cats.

Research conducted in more densely populated areas, or areas where unowned cats aren't entirely reliant on prey for their meals, reveals predation rates far lower than 80 percent, [12] especially for birds.

Despite the scarcity of direct observations, evidence for the existence of large arctic cod aggregations in winter was traditionally derived from the intensive predation rate estimated from the stomach content of marine mammals and birds later in the season (Welch et al. 1992).

Said Legge, «Our study highlights the scale and impact of feral cats,» logically at about 10 % the rate Hunt earlier projected, or even as little as 2 %, adjusting for predation rates in the realm of actual cat hunting behavior, «and the urgent need,» Legge continued, «to develop effective control methods, and to target our efforts in areas where control will produce the biggest gains.»

In their recently released book, The American Bird Conservancy Guide to Bird Conservation, ABC changes tack a bit — using what the authors call «conservative» estimates of the outdoor cat population and annual predation rates, for example, to arrive at their figure of «532 million birds killed annually by outdoor cats.»

By using inflated predation rates — the result of some peculiar, unjustified assumptions — they virtually buried the most important findings of their study.

So, whereas Dauphiné and Cooper (and others) suggest increasing such estimates by factors of two and three («predation rates measured through prey returns may represent one half to less than one third of what pet cats actually kill...» [14]-RRB-, they should, in fact, be reducing them by half.

In fact, David Barratt found this kind of guesswork to overestimate predation rates.

«You can argue that the animals that are affected by rodenticide are weaker,» Thompson says, «and that the predation rates on them, as I suspect, are higher.»

The researchers used a global distribution map of these species, included data on their morphology and reproductive rate, and estimated predation rate.

«This is the first illustration that the spiders could also use the chemical cues to try to decrease the predation rate and also increase the attraction of prey,» says I - Min Tso of Tunghai University in Taiwan, who wasn't involved in the study.

During the same period, predation rates — the proportion of the moose population killed by wolves — also dropped to the lowest ever recorded, while the number of moose doubled, to approximately 1,050 moose.

At a larger scale, this method would more accurately assess the seasonal variation in predation rates, individual hunting behavior throughout the year and the actual impact of cat predation on prey populations (Tschanz et al., 2011).

This study found that many cat owners overestimate their cats» predation rates.

The study shows a predation rate by the cat that is rather appalling.»

Cats and Rodents The fact that scats indicated rodents were predated to a greater extent than birds is hardly surprising [5, 6, 9, 10], but it should be noted the 65 % figure represents the frequency of occurrence, and not a predation rate (a topic I address in greater detail here).

«In Illinois, George (1974) found that only about half of animals killed by cats were provided to their owners, and in upstate New York, Kays and DeWan (2004) found that observed cat predation rates were 3.3 times higher than predation rates measured through prey returns to owners.

There are some minor differences between their method for estimating predation rates and mine.

The two inflated figures described in (1) and (2) are multiplied together, further inflating estimated predation rates.

So, even setting aside the complexities of source - sink dynamics, these inflated predation rates, combined with the fact that «the estimates of breeding density presented in this manuscript should be regarded as minima,» [3] raise serious doubts about whether the site is in fact a habitat sink (or, if so, to what extent).