University of Chester

Do racing pigeons (Columba livia domestica); have a colour or calorific preference?

A DISSERTATION SUBMITTED TO THE UNIVERSITY OF CHESTER FOR THE DEGREE OF: ANIMAL BEHAVIOUR AND WELFARE BI6110 – 2012/2013 Department of Biological Sciences Student: Yasmin Bailey Supervisor: John Cartwright

Word Count

Abstract 327 Main Body 8346

DECLARATION

I certify that this work is original in its entirety and has never before been submitted for any form of assessment.

The practical work, data analysis and presentation and written work presented are all my own work unless otherwise stated.

Signed …………………………………………………………….

Yasmin Bailey

Page 1 of 44

Abstract

Pigeon racing was immensely popular amongst male industrial workers in the nineteenth and early twentieth centuries (Johnes, 2007). This study offers an overview of pigeon racing in this period, before moving on to discover if racing pigeons (Columba livia domestica), have a preference to their food; and if so, could this help the pigeon racers of today? The subjects used in this study consisted of eight racing pigeons (Columba livia domestica) , four cocks and four hens all around the same age of 28 days. The experiments carried out were split into three parts. Experiment one involved colour preference, where the pigeons were given a different colour feed each day, for ten days. The second experiment involved colour preference again, however the pigeons were given a mixture of all five colours of feed, blue, red, green, yellow and natural, for another ten days. Experiment three then moved onto see whether pigeons have a calorie preference, so they were given a high calorie diet one day, a low calorie diet the next and then a mixture of both high and low calories the following day, causing a sequence that continued for twelve days. During these experiments the temperature was also recorded at the feeding times of 8am and 4pm. This concluded that the pigeons ate more when it was warmer. These results seemed unusual, as it was presumed they would eat more when it was colder, to keep themselves warm. Further findings during these experiments established that the racing pigeons prefer the colours red and natural in their foods, this was statistically found in experiment two; which also showed that they least prefer the colour green. These experiments could lead to further research, to see whether pigeons that eat a high or low calorie diet, increase their racing speed, or travel further in races. The calorie foods could be tested again, however they could be dyed red to see if the pigeons preference changes, or instead of using colours, flavourings could be used instead.

Page 2 of 44

Contents

DECLARATION ...... 1 Abstract ...... 2 Acknowledgements ...... 4 1. Introduction ...... 5 2. Materials and Methods ...... 10 2.1 Housing ...... 10 2.2 Food and Colours used ...... 11 2.3 Other materials used ...... 12 2.4 Experiment One Procedure ...... 12 Preliminary Study ...... 12 Main Study ...... 13 2.5 Experiment Two Procedure ...... 14 2.6 Experiment Three Procedure ...... 15 2.7 Temperature ...... 17 2.8 Statistical analysis ...... 17 3. Results ...... 19 3.1 Experiment one: Colour preference results ...... 19 3.2 Experiment Two: Colour preference results ...... 20 3.3 Experiment Three: Calorie preference results ...... 21 3.4 Experiment Three: Calorie preference results ...... 22 3.5 Temperature – Experiment one ...... 23 3.6 Temperature – Experiment two ...... 24 3.7 Temperature – Experiment three ...... 25 4. Discussion ...... 26 4.1 Experiment One and Two ...... 27 4.3 Temperature ...... 31 4.4 General Discussion ...... 33 5. Conclusion ...... 35 6. References ...... 37 7. Appendix ...... 44

Page 3 of 44

Acknowledgements

This study was inspired by the British Homing World in relation to the Royal Pigeon Racing Association, hoping to help the pigeon racers of today find new tactics for winning the national races. Fantastic support was given to me from my supervisor, John Cartwright and I am very thankful to Wirswall Farm, for the facilities of their pigeon loft and racing pigeons. Family and friends, especially my sister Jo, have given me great support and kept me motivated.

Page 4 of 44

1. Introduction

Racing homing pigeons (Columba livia domestica), is a worldwide sport (Hagstrum, 2000), that consists of different variables, in order to achieve success with the winning pigeon(s). This sport is very competitive and requires a lot of day to day training. The racing season is between April and September; however, pigeon fanciers are concerned about the overall health of their pigeon flock all through the year (De Herdt & Pasmans, 2009); particular time and care is spent pairing them for breeding, to acquire the best possible racers.

Factors that affect race performance in pigeons include nutrition, husbandry, training, physical ability, and general health of the race team (Rupiper, 1998). Racing pigeons involves feeding the birds the correct amount of protein, vitamins and fats but also allowing them access to grits and minerals (Brakstad & Raaholt, 2009). These help them through the different stages of, racing, moulting and breeding. In the first year of their life, they can be prone to many diseases (Alexander, 2011), one of which is very common called young bird sickness. This condition has been characterised by slow crop emptying, weight loss, poor performance (Scullion & Scullion, 2007) and much more; which is why it’s important a racing pigeon’s diet is balanced in terms of nutrition, to give strong health for the racing season.

It is evident that pigeons fly back to their homes, where they know and feel, they are well looked after. Pigeon racers have to abide by the Animal Welfare Act 2006 (Defra, 2013).Which states that they must be giving the pigeons a suitable place to live, a suitable diet with access to fresh water, the ability to express normal behaviours, have protection from illness or injury and the need to be housed separate or with other animals. Temperature and lighting are also main priorities for pigeons, especially through moulting season to make sure they have the sufficient feathers for flying (Cousquer & Parsons, 2007). The variables and necessities of the pigeon’s welfare generated ideas towards this study. Do pigeons have a preference and if so, what? A solution to this study may also give useful information to magazines such as,

Page 5 of 44

the Royal Pigeon Racing Association (Higgins, 2013) and give suggestions to pigeon fanciers.

Experiments involving colour preference have been looked into previously by many authors; however they involved the same method. Zentall & Singer, (2007), and Clement & Feltus, (2000), took out two separate experiments that involved the pigeons pecking a white light either 1 or 20 times. If they got that correct they had a colour test, where they then had to choose the correct colour to receive food. The colours used were decided from previous training, two colours the pigeons liked and always went to, and two colours they weren’t so bothered about. These tests were completed seven years apart and both had the same outcome. The pigeons showed a preference for the colour that followed the greatest effort during training (Lydall, 2010), suggesting that pigeons like to work for their food, their colour preference during these trials was red. These experiments stimulated more curiosity for further research, to see what colours pigeons truly preferred, if given a larger choice.

As well as this, Biedermann & Garlick, (2012), investigated food preference in pigeons. The pigeons were presented with six novel foods, ranging from high calorie to low calorie with a variety of foods having a calorific content between these. The food was weighed before and after each session; the outcome showed pigeons preferred the high calorie foods. In the mentioned study the amount of different sample feeds was six, which is quite a large number to use within one trial. This inspired experiment three in this study. If they were only given the choice of one high calorie food and one low calorie food, would the outcome be different?

Pigeons have excellent visual capabilities, which is why there’re particularly used for investigations of visual, categorization processes (Dittrich L. , 2009). As pigeons have sophisticated colour vision, they may use colour cues for discrimination of ‘good’ foods (Watanabe & Masuda, 2010). Their colour vision is also known to be pentachromatic (Dittrich, Adam, Ünver, & Güntürkün, 2010), which means they have more than four cone classes in their retina (Pike, 2012), located at the back of the eye

Page 6 of 44

(Klemas, 2013). Many studies that have been completed involve the use of coloured lights, to establish if the pigeons could understand the different colours (Leising, Garlick, Parenteau, & Blaisdell, 2009). As pigeons are able to identify different colours, it is almost certain they will have a colour preference to their food. This research could benefit the racer as well as the pigeon, simply because when the pigeons are racing home, they can pick out different coloured landmarks, to help with their sense of direction (Knight, 2011).

Temperature was also looked into in this study, to discover if it has an effect on the amount the pigeons ate in the morning. Previous research has been done, putting pigeons in living conditions with temperatures of 6°c, 1°c and 0.6°c with food and water available, however they would have to peck twelve times in order to get the food (Henderson, 1992). The outcome of this research showed the colder it was the more the pigeons ate. Another study was done on fasting pigeons in cold temperatures and giving them different environmental cues, such as predator stimulation. The outcome of this showed that even with the different environmental cues, the pigeons were still capable to adjust their thermoregulatory function (Laurila, 2005), so if they realised there was no food accessible to them, they can keep their body temperature in reasonable boundaries, to keep fit and healthy until they find some.

A pigeon can lose up to one third of its body weight in a race (Walker, 1988), so this has to be dealt with as soon as the pigeons arrive home. If this research has an outcome with sufficient data, then pigeon racers will be able to use it, to help them to win races, by giving the pigeons food which provides them with enough energy to last the entire journey home, and get them into the lofts quickly to recuperate. If racers find a suitable type of feed that works, to give the birds enough vitamins, minerals and energy, but they then struggle to get the pigeon to eat all the food to give them what they need to race to their full potential, they could colour the food with the preferred colour shown in the experiment and encourage them to eat more. This study could also help to get pigeons into the loft at the end of a race as quickly as possible. Pigeon racers have many different techniques to return their birds into the loft, one of these

Page 7 of 44

consists of shaking a tin of food to attract them, but it could be beneficial to know there is a quicker trailed and tested method that guarantees good results. Zentall, (2010), found that pigeons will work to get their food, so if the racers were to have fed the pigeons their preferred coloured food before they went to the race, then shake the tin when they arrive home, the pigeons may become quicker at getting inside the loft, as they know they will receive the food they enjoy, but they would also need to learn to recognise this noise, so they need to hear this at feeding time too.

Hypothesises:

The hypotheses that will be investigated within this study are:

Experiment 1 and 2 – Colour preference of food

H0 - Racing pigeons will not have a colour preference to their food.

H1 – Racing pigeons will have a colour preference to their food.

Experiment 3 – Calorific preference to food

H0 – Racing pigeons will not have a calorific preference to their food.

H1 – Racing pigeons will have a calorific preference to their food.

Experiment 4 – Temperature effects

H0 – Temperature will not affect the amount of food the racing pigeons eat.

H1 – Temperature will affect the amount of food the racing pigeons eat.

This study may also lead to other experiments involving colour preference. These may include, painting the lofts on the inside or outside of the pigeons preferred colour. Having it coloured inside may relieve any stress the animal may have as it would feel safe and comfortable in its own environment (Costantini, 2010). Instead of using colours in their feed, flavours could be added instead. These could consist of vanilla, cinnamon, coffee and many more. Changing the location of where the pigeon is fed may also help them eat all the food. When being fed the same food in the same place

Page 8 of 44

the animal will habituate to this routine, however if the food was to be placed in a different area, it would keep the pigeon open minded to where it may be fed next, as in the wild they would have to search for food. Pecchia, Gagliardo & Vallortigara, (2011), used different coloured pipes within an enclosed arena, which also involved spatial cognition, as the pigeon’s had to find which coloured pipe had the food inside it. This could be linked to colour preference by having food under all four pipes, measuring which colour the pigeons went to first and last or not at all. These types of studies can also link into, feeding the pigeon within the different seasons (Vriends, 2005); to see if that has an effect on the pigeon’s preference of colour, flavour or area of feeding in the loft.

Page 9 of 44

2. Materials and Methods

2.1 Housing

Eight young racing pigeons were used for this study, being fed twice a day at 8am and 4pm; to ensure there was enough daylight, (Yahner, 2012), for the subjects to explore their feeds adequately. Experimenting with young racers was vital as they have never experienced different types of feed or coloured foods before (Guilford, Åkesson, Gagliardo, & Holland, 2011). The eight pigeons consisted of four hens and four cocks at 28 days old equipped with numbered leg rings for individual identification (Zimmerman, 2009).

The pigeons had eight individual boxes to sit and be fed in within the loft (Watanabe & Masuda, 2010). As well as this they had perches around the sides, plenty of space to fly around and a water trough on the floor. The perches around the side gave them the opportunity to roost at night and express their natural behaviours (Meade, Biro, & Guilford, 2006). Experiments have shown that a sizeable amount of food empties from the crop, while pigeons are inactive during the night (Rashotte M. E., 1997). With this research taken into consideration the loft was big enough for the pigeons to fly around in through the day, so they would burn off some energy before being fed again in the afternoon. Having just the perches and boxes, was also designed so that it was easy to maintain (Hawkins, 2010). This involved scraping them out every morning to keep them clean. Fresh water was accessible for them at all times, and other authors used grit within enclosures as well (Reilly, Posadas-Sánchez, Kettle, & Killeen, 2012). Grit can help with enrichment through the day but also help breakdown their food (Green, Myerson, Holt, Slevin, & Estle, 2004); however in this case to keep the research non- bias, grit was not used.

The data was collected during the winter months, so low temperatures were expected. The temperature was natural with no added heating, however the temperature was monitored and recorded before the morning and afternoon feeds with the use of a

Page 10 of 44

thermometer, that was kept in their at all times. Having a natural temperature would help the young birds build a strong immune system, (Bahrami, 2012), as having the environment to warm can cause disease or parasites. The lighting was also kept natural with a small vented window, with other vents around the loft as well (Rupiper, 1998).

2.2 Food and Colours used

To discover if the young racing pigeons have a true colour preference, two different food colour experiments were taken out, to bring conclusions to questions posed. The five colours, used in both tests were: red, blue, green, yellow and natural, these were individually mixed with plain wheat seeds. This is similar to Schmidt & Schaefer (2004), who gave blackcaps, ( Sylvia atricapilla) the choice of five colours to find their preference. The plastic food pots used were, 8cm long and 4cm wide, enabling a maximum of 170g, which wouldn’t be necessary for these experiments; however the large capacity pot was used, so the pigeon was able to view everything inside.

Some colours were decided from the colours of pigeon corn, these being yellow, natural and red; as they may be related to selection for carotenoid-rich foods suggested by Senar, et al., (2010), which is what pigeons would forage for in the wild. However the other colours were used due to different author research. Many authors found that pigeons prefer blue (LoBue, 2011), which is unusual as it’s not in their natural feeds. Lazareva (2005), used green and red due to them being very different colours as so did Mazur (2010), for the same reasons.

Morrison’s liquid food colouring was used to colour the wheat. 152ml of food colouring was mixed to 5500g of wheat for each colour to ensure there was enough feed for both experiments (Larrinaga, 2010), and that the colours were bright enough to see a difference, when all placed in the same feed pot. This had to be correct as if the colour is brighter or duller the reaction of the pigeon’s eating the food may vary through the data. For the colour natural, the wheat seeds were kept plain. All the food

Page 11 of 44

colourings used are tasteless (Kim, Garner, & Millam, 2009) and odourless (Mora, Davison, Wild, & Walker, 2004), to prevent any bias data, such as, the pigeon’s choosing one particular colour due to the taste or smell, and will also prevent any harmful effects. However further research could involve studies investigating whether different tastes or smells, have an effect on the pigeon’s preference to their feed.

The third experiment consists of low and high calorie foods. The high calorie food used for the experiment entailed sun flower hearts and the low calorie food used consisted of barley. Biedermann & Garlick (2012) used sunflower hearts which they found were most consumed, when experimented against a low calorie food as well. This is why it was tested in this experiment, against barley, a food source that is in many different pigeon corn mixes (Diarra, Usman, Igwebuike, & Yisa, 2010).

2.3 Other materials used

• 16 food pots, 8 for am, 8 for pm • Water trough • Thermometer • Weighing scales • Marker pen – to number the feed pots • Legs rings – numbered 1-8 for identification • Food dye, blue, red, green and yellow • Foods, wheat, barley and sunflower hearts • Tools for cleaning their boxes out

2.4 Experiment One Procedure

Preliminary Study

Before the initial experiment was carried out, a preliminary study, over a two day period, was completed. The preliminary study was used to provide information on

Page 12 of 44

how much food the racing pigeon’s should be given for each feed. Racing pigeon’s usually consume 30-40 grams of food a day (Powers, 2002). The eight racing pigeon’s will need to consume this amount over two separate feeds. The pigeons were given 20g of red wheat in the morning at 8am for 30 minutes and 20g of red wheat in the afternoon at 4pm, for 30 minutes (Strasser & Bingman, 1999), which was monitored with the use of a stopwatch. This was then repeated the following day, using the colour blue instead.

The preliminary study showed that the intake of food should be increased. This is due to the pigeon’s eating all the food given both times. To achieve the best results, more food would encourage them to have left over food, which could determine a more positive effect towards certain colour preference. They also require a minimum of 40g a day, ensuring they have plenty of energy, due to the data being collected during their moulting period (Costantini, 2010).

Main Study

Experiment one consists of the pigeons being fed a different colour grain every day, for 10 days, allowing the five colours to be presented twice to the pigeons (Hartley, 2000). The pigeons were caught and secured into their individual boxes (Costantini, 2010). When the pigeons are closed into their boxes, they are unable to see one another, putting all their focus on their feed pots. The temperature of their enclosure was recorded, morning and afternoon before the pigeon’s received their food, and fresh water was given and placed on the main floor of their enclosure. The food was prepared outside the loft so the pigeons were unable to see what they were going to receive.

Green was the designated colour for the first day of the trial, as Roper, (1997) suggested; it was an intermediate colour preference, which may be due to it being a colour they are familiar with, but don’t see all the time. A total amount of 26g, of green wheat was weighed out into individual numbered feed pots, for all eight pigeons

Page 13 of 44

for their morning feed at 8am. This was then placed into their boxes (Lubyk & Spetch, 2012), and left there for 30 minutes (Bordel & Haase, 2000). Mehlhorn & Rehkamper, (2009), suggests that orientation of the food pot could be another variable for further research to see if this changes the pigeon’s preference to what it chooses to eat. A recent study has been completed on pigeons being given the choice of the same food in two separate food pots, within their boxes to see which area they preferred to eat their food in (Lubyk & Spetch, 2012).

After the 30 minutes, of the pigeon’s food being presented to them, the feed pots were removed and the birds were released back into the rest of their enclosure. The weight of food left in the numbered feed pots was recorded for each individual pigeon on a separate recording sheet specifically for them, and any reaming coloured wheat was thrown away. The feed pots were washed between all feedings with warm water to prevent any bias (Skelhorn, 2011).

The same process was completed again for the afternoon feed (at 4pm), using the colour green, the amount of food which was left for them was again 26g, and as the morning feed, it was left for the duration of 30 minutes. The following day followed the same method, but using a different colour, which was yellow. Each day within the ten day period involved a different colour, the sequence of colours was: green, yellow, natural, red, blue, and this was repeated once more. Once experiment one had run its course, the pigeons went straight onto experiment two.

2.5 Experiment Two Procedure

This experiment involved a similar process as in experiment one, however it involved feeding all the colours of grain at the same time, twice a day, (Ulrich & Prior, 1999), at 8am and 4pm. It was carried out over a period of 10 days and used the same method of catching the pigeon’s and placing them in their boxes (Costantini, 2010); the temperature of their enclosure was recorded morning and afternoon, fresh water was given, and their food was prepared outside the loft.

Page 14 of 44

Homing pigeons are known to have favourite foods which they will selectively pick out when given a corn mixture feed (Thalau, Holtkamp-Rötzler, Fleissner, & Wiltschko, 2007). This initiated the thought to putting all the different colours of grain into their numbered feeding pots, so they were able to selectively pick out which colours they wanted to eat, making a colour choice (Borgia & Keagy, 2006). It could also be presumed that the pigeon’s will select the colour that experiment one stated as their preferred colour (Barta, Liker, & Mónus, 2004). Emmerton, (2001), discussed how the pigeon’s varied from 10 minutes to 30 minutes in the length of time they took to choose the different colours, which helped assure 30 minutes feeding was long enough.

For the first five days of the experiment 6g of each of the five different coloured grains, (giving a total of 30g at each feed), was given at 8am and 4pm. However, it was found that after the 30 minutes, a lot of food was leftover; displaying this was too much food for some of the pigeons to eat in one day (Vriends, 2005). For the remainder of the five days, they were given 3g of each colour, (giving a total of 15g at each feed) during their morning and afternoon feed times of 8am and 4pm.

When the feed pots were collected after the 30 minutes, the coloured wheat grains are weighed individually for each pigeon. This was then recorded on the pigeon’s individual weight sheets, where the temperatures were also noted, any remaining food was thrown away, and the food pots being washed for the next feeding time (Skelhorn, 2011).

2.6 Experiment Three Procedure

Experiment three consists of using two food types, a high calorie feed consisting of sunflower hearts, and a low calorie feed, which is made up of barley (Biedermann & Garlick, 2012), this was carried out over 12 day period. This allowed four days each for barley and sunflower hearts to be fed separately and four days for them to be fed

Page 15 of 44

mixed together, to gain significant data to hopefully show a preference in the pigeon’s feeding choice. During this experiment it was required that the temperature was taken at both feeding times for the 12 days, the birds were provided with fresh water and it was ensured the food was prepared outside the loft.

Sunflower hearts have been used in previous experiments to see if Black-capped chickadees (Poecile atricapillus) , had different foraging strategies when presented with novel foods, (Yong, Buddhamas, & Newman, 2011) and an experiment with grainivorous birds, to see if they had a preference when presented with a number of different types of seeds (Joshua & Ali, 2011).

The feeds were prepared and 28g of barley was fed on the first day at 8am and 4pm, with the same routine as in experiments one and two, where the food was placed in the pigeon’s box and leaving it for 30minutes, before it was removed and releasing the pigeons into the rest of their enclosure. Once removed, the weight of the food left over was recorded and the food pots were washed, (Skelhorn, 2011), ready for the next feeding time. The following day the pigeon’s would receive the sunflower hearts instead of the barley, again 28g at each feeding time, following the same routine.

The third day however consisted of the pigeon’s receiving 28g of barley and 28g of sunflower hearts in the same food pot mixed together. When the food was taken away after 30 minutes, the barley and sunflower hearts were weighed separately for each pigeon and recorded.

Any remaining food that was thrown away must be thrown into a secure bin to prevent larger animals, such as cats, foxes and rats eating them. These animals being around can cause risk to the experiments, as they are capable of getting into the loft and killing the racing pigeons (Weber, 2011). Other prevention methods in place to secure the pigeons from predators, involve locks on the loft doors and all the coloured wheat, barley and sunflower hearts tubs, are locked in a separate shed.

For all three experiments, the food, whether it is coloured, high or low calorie, will be weighed to monitor how much the pigeon’s ate over the period of time the

Page 16 of 44

experiments were carried out. To measure the weight of the food before and after, a set of food weighing scales will be used to record the amount in grams (g), (Bauer, Glassman, Cyr, & Romero, 2011).

2.7 Temperature

For all three experiments the temperature was recorded at 8am and 4pm, with the use of a thermometer, which measured the temperature in Celsius, (°C) . As the data is being collected in the winter months, it would be interesting to find out, if pigeons ate more when it was colder. Wild pigeons (Columba livia), are known to eat more when it’s colder during winter time, because they have learnt that the food source availability is low during this time (Carrascal, Seoane, & Villén-Pérez, 2012). As the subjects are only 28 days old at the start of the experiments, they will still be learning and developing. When fully gown they should be capable of knowing their predators, exposure to knew pathogens and climate change (Geiser, 2013). This can also lead to further experiments with older racing pigeons to find if fully matured pigeons eat more when it’s colder.

2.8 Statistical analysis

The statistics that will be used will vary depending on the experiment. The level of significance that will be used for all the data is 0.05. The data from experiments one and two will measure which colour was preferred from the racing pigeon’s, by measuring the amount consumed of each colour. This would involve either a Kruskal- Wallis Test or a One-way Anova Test (Friedrich & Zentall, 2004), depending on if the data is found to be normally distributed or not. This data will be presented using box- plot graphs.

The data collected from experiment three will measure how much barley and sunflower hearts were eaten, when fed together and separately. For both parts of this data, a Paired-Samples T-Test or a Wilcoxon Test will be used, depending if the

Page 17 of 44

Kolmogorov-Smirnov Test, reveals if the data is found normally distributed or not. These results will be displayed using box-plot and bar chart graphs.

The data collected for temperature, will be measured to see if it had a significance to weather the pigeon’s ate more or less of the foods given to them in experiments one, two and three. Depending if the data is normally distributed or not, the test used will either be a Spearman’s Correlation or a Pearson’s Correlation. These results will be shown using scatter and box-plot graphs.

Page 18 of 44

3. Results

3.1 Experiment one: Colour preference results

A Kolmogorov-Smirnov Test was completed to test if the data would be normally distributed. As this set of data was non-parametric a Kruskal-Wallis Test was performed. This showed there was no significant difference, that the racing pigeon’s had a colour preference to their food, (X 2=2.638, df=4, p=0.620). If the data was significant, research would be carried out to look at the key colours, using pairwise tests. Figure 3.1 shows the minimum amount of food that was eaten of each colour, but doesn’t show the maximum amount of food eaten, due to the insignificant data.

Figure 3.1. The box plot graph shows the amount of coloured food that was consumed from all eight pigeon’s over the 10 days. No significant difference was found.

Page 19 of 44

3.2 Experiment Two: Colour preference results

To establish the results for experiment two, a Kolmogorov-Smirnov Test was used to test if the data would be normally distributed. The outcome showed the data was non- parametric; therefore a Kolmogorov-Smirnov Test was performed. The outcome of this test showed a significance for pigeon’s having a colour preference, (X 2=202.43, df=4, p=0.000). The test also revealed five statistic’s for the amount of each individual colour that was eaten, (R=0.202, B=0.208, G=0.215, Y=0.170, N=0.178). Figure 3.2 evidently shows the racing pigeon’s least preferred green.

Figure 3.2. The boxplot graph shows the amount of coloured food that was eaten, when presented with a choice of all five colours in their food pot. A significance was found, resulting in green being their least chosen colour and red and natural being their most consumed colour.

Page 20 of 44

3.3 Experiment Three: Calorie preference results

The results were split into two sections. Firstly, results were established for when barley and sunflower hearts were fed separately, including both am and pm feeds. A Kolmogorov-Smirnov Test was used to test if the data would be normally distributed. This test showed that the data was parametric; therefore a Paired-Samples T-Test was used. The T Test revealed there was a significance, that sunflower hearts were consumed more than barley, (T=-26.250, df=127, p<0.001). If the data was non- parametric a Wilcoxon Test would have been used. Figure 3.3 shows that the barley was consumed in varied amounts, with the pigeons eating as little as nothing (0.00g), or eating all of it (23.00g). However it shows the pigeon’s always ate some of the sun flower hearts from as little as (11.00g) to all of it at (23.00g).

Figure 3.3. The box plot graph shows the amount of barley and sunflower hearts consumed, when the pigeons were fed individually on separate days.

Page 21 of 44

3.4 Experiment Three: Calorie preference results

Section two involves the results for when barley and sunflower hearts were fed mixed together, including both am and pm feeds. A Kolmogorov-Smirnov Test was used, to test if the data would be normally distributed. This test showed the data was parametric and so another Paired-Samples T Test was performed. This T Test showed the data was significant and that the pigeon’s picked out the sunflower hearts more over the barley when given the choice, (T=-48.996, df=127, p<0.001). If the data was not significant a Wilcoxon Test would have been used.

Figure 3.4. The bar chart graph shows the mean of the total amount of food eaten by the eight pigeons, including their am and pm feeds, when barley and sunflower hearts were fed mixed together.

Page 22 of 44

3.5 Temperature – Experiment one

A Kolmogorov-Smirnov Test was used to test if the temperature data for experiment one, would be normally distributed. This revealed the data was non-parametric; therefore a correlation was done using Spearmen’s. The correlation discovered the data was very nearly significant from a one-tailed test and that the pigeon’s ate more when it was warmer, (r s=0.214, p>0.05).

Figure 3.5. The box plot graph shows the warmer the temperature, the more food the racing pigeon’s ate, when they were fed a different colour each day, for ten days.

Page 23 of 44

3.6 Temperature – Experiment two

A Kolmogorov-Smirnov Test was used to test if the data for the temperature would be normally distributed. The outcome showed the data was parametric, so a correlation was done using Pearson’s. This correlation showed significant data, displaying pigeon’s ate more when it was warmer, (r=0.474, p<0.001).

Figure 3.5. The scatter graph shows the warmer the temperature, the more food the racing pigeon’s ate, when fed all five colours mixed together over ten days.

Page 24 of 44

3.7 Temperature – Experiment three

A Kolmogorov-Smirnov Test was used to test if the data for the temperature would be normally distributed. This data was shown as parametric so a correlation using Pearson’s was used. The outcome of Pearson’s Correlation showed the data was not significant (r=-0.110, p>0.385).

Figure 3.5. The scatter graph shows no significance was found with the temperature, when the racing pigeons were fed barley and sunflower hearts, over the twelve days.

Page 25 of 44

4. Discussion

The aim of the study was to determine if racing pigeons have a colour or calorific preference to their food. Results showed that they do have a preference for colour, when they are able to selectively pick out their chosen colour, and they prefer high calorie foods, and will consume as much of it as they can, when its provided.

The eight subjects used (Watanabe & Masuda, 2010), were similar ages at around 28 days old. When weaned from their parents, they had to learn for themselves, in order to survive including, finding ways to eat and drink. Pigeons kept in groups can display delicate, local interactions among group members (Nagy, Ákos, Biro, & Vicsek, 2010). This could possibly proclaim that the racing pigeons may copy each other, or make a decision from what other group members are doing. When the data was collected the pigeons were in separate boxes, unable to see each other. Further studies could be carried out to see if food preference changes, when pigeons are able to interact with each other while eating their food.

A recent study discussed how two racing pigeons housed together, were taken to a different area and released to fly home; this revealed an outcome that, both pigeons used separate routes to get home, possibly showing that they have a different preference to their journeys home, (Flack, Pettit, Freeman, Guilford, & Biro, 2012), therefore they may have different preferences to their food, when able to interact together. The three experiments do not pressure the pigeon’s to eat, as they can leave or eat as much as they like. It may be interesting to consider what results could be found, if the same three experiments were carried out, using adult racing pigeon’s as the subjects (Garlick, Gant, Brakel, & Blaisdell, 2011). Adult racing pigeon’s may have more of a preference as they would have experienced different food colours through their lives, (Mora, Ross, Gorsevski, Chowdhury, & Bingman, 2012).

Using racing pigeons as the subjects to carry out the experiments requires additional thinking to the methods. The three sets of data could have shown more or less

Page 26 of 44

significance if the pigeons were able to carry out their daily routine of exercise (Humphreys, Carrington-Cotton, & Wernham, 2010). The only exercise available during the collection of the data was flying around their enclosure, which could be seen to prevent bias, but releasing them outside for exercise may have resolved in the pigeons hitting electric wires and causing themselves injury, or resulted in being captured by predators (Dixon, 2002).

Having a large sample size could help restrict the racing pigeons from being kept inside, Dell’Ariccia, Dell’Omo, & Lipp (2009), had a sample size of 40 racing pigeons and was able to let them fly outside the lofts, as enough data would still be generated, if the sample size was to slightly decrease. Also, flying the pigeon’s before feeding will allow them to all be hungry at the same time, (Mora, Ross, Gorsevski, Chowdhury, & Bingman, 2012), as exercise will create hunger because they are using energy. However, bias data could still be collected, due to weather conditions. With bad weather conditions, such as rain or snow, racing pigeons should not be put out for exercise. This is simply because the pigeon’s will not fly, and will just land on top of the lofts (Walcott, 1996); where they are more susceptible to predators.

4.1 Experiment One and Two

Experiments one and two consisted of the same hypotheses, as they were both used to test for colour preference. Experiment one’s results showed no significance (X 2=2.638, df=4, p=0.620), indicating that a null hypothesis should be accepted. This means that the racing pigeon’s had no colour preference to their food. The pigeons were fed one set colour per day, which the pigeons may have eaten as they knew it was the only food they would receive, and no matter what the colour was, it was always followed, by equal conditions of reinforcement (Friedrich & Zentall, 2004).

Improvements to experiment one’s methods, may involve the amount or type of food and length of time the pigeons had to eat. Wheat grains were dyed (Moran, 1999), due to them not having much colour naturally, which made them easy to dye the five

Page 27 of 44

individual colours. Organic wheat grains are the same colour consistency; however the conventional wheat grains are richer in protein (Coelho, 2010). McKenzie & Whittingham, (2010), found that previous experiments for food preference, involving organic and conventional foods in birds, needed more experimental time, to allow the birds to explore the foods more. With this in mind, an experiment was set up to find if twelve Canary birds (Serinus canaria domestica), had a food preference over a period of fourteen days. They were given the choice of two bowls, one consisting of organic wheat grains and the other consisting of conventionally grown wheat grains. The birds were then observed and recorded for the amount of times each bowl was pecked. Overall the birds preferred the conventional grain, but it takes time for the birds to tell the difference between the two food types (Coelho, 2010). This may show why experiment one, resulted in there being no significance towards the pigeon’s having a colour preference of their feed, this may be due to the amount of time they had to eat the food. Simply because conventionally grown wheat grains were used in the experiment (McKenzie & Whittingham, 2010), however the pigeons may have recognised they were receiving different colours each day, but needed more time to explore them.

The feed on the other hand could be changed to help improve this method. Biedeman & Garlick, (2012), researched food preference in laboratory pigeons. They presented the pigeons with six novel foods, consisting of, granulated peanuts, popping corn, freeze-dried mealworms, bread crumbs, split peas and sunflower hearts. The outcome showed that sunflower hearts were preferred, followed by popping corn and granulated peanuts. Killeen, Cate & Tran, (1993), also found through their experiment that pigeons prefer peas and popcorn. This research could improve experiment one in this trial by using popcorn instead of wheat, as it would still be easy to dye different colours, however, peas would be difficult to colour as there’re already a dark shade.

Experiment two’s data involved a Kolmogorov-Smirnov Test to determine the results, which showed a significance, (X 2=202.43, df=4, p<0.001). This means the pigeons do have a colour preference to their food, so the null hypothesis is rejected, and the

Page 28 of 44

alternative is accepted. From the box-plot graph (Figure 3.2), it shows that red and natural were preferred a lot more than the colour green.

Wild birds consume coloured foods such as reds and blacks during the winter months (Honkavaara, Koivula, Korpimäki, Siitari, & Viitala, 2002). Red maize can also be found in many different pigeon corn mixes. Black on the other hand is not a common colour within the pigeon corn mixes, but some foods such as peas are a dark green, shade of colour (Adebayo-Oyetoro, 2012). It could be said that the racing pigeons ate what they usually would during the winter time, however this wouldn’t match the results found from experiment two, simply because the coloured food was wheat which they can eat all year round.

To find a true pigeon’s colour preference the same food could be used, such as natural wheat, but the food bowls could change colour instead. This would involve the same method, feeding them certain amounts and weighing the food after, but it may conclude a different colour preference result. Strasser & Bingman, (1999), did an experiment with pigeons; giving them different coloured food bowls to see if they remembered the different colours, this indicated that pigeons can recognise the different colours, so they should have a preference in their food, unless they are not bothered because whatever colour they have it tastes the same. Other experiments that could be carried out, to find if pigeons can distinguish different colours could be to use different coloured lights in their enclosure at feeding times (Kelly & Grant, 2001). An experiment was taken out using broiler chickens (Gallus gallus domesticus) , and was found that they showed a different response to coloured lights, it showed a strong dislike for the colour green (Priel, 2007).

Improvements for experiment two could include using the same food and colours but altering the times being fed. They could be fed smaller quantities, but more times though the day. Some research has shown that their racing pigeons when given large amounts of food would only eat small amounts (McLean, 1972). Small amounts may also allow the pigeon to identify the different colours more clearly.

Page 29 of 44

Pigeons also need water after at least half an hour after eating (Vriends, 2005), this could also be an improvement that could be made to experiment two, as they could have water in their individual boxes as well as their food, to see if them being able to eat and drink at the same time makes the pigeons consume more or less or have a change in preference

4.2 Experiment Three

Experiment three’s results consisted of two parts, section one was completed using a Paired-Samples T-Test, which showed a significance (T=-26.250, df=127, p<0.001). It was clear that when the barley and sunflower hearts were fed on separate days, that the high calorie food, sunflower hearts was most preferred (See Figure 3.3). This means that the racing pigeons do have a calorific preference to their food, so the null hypothesis is rejected, and the alternative is accepted.

The second part of the results involved testing to see which food was most consumed when barley and sunflower hearts were mixed together, giving the racing pigeons a choice. A Paired-Samples T-Test was completed, which showed a significance (T=- 48.996, df=127, p<0.001). This also indicted that the pigeons had a preference for sunflower hearts (See Figure 3.4), so the null hypothesis is rejected and the alternative is accepted.

Previous experiments have been done on food preference in racing pigeons which involved a food source of sunflower hearts as well as 5 other novel foods (Biedermann & Garlick, 2012). This research also indicated that sunflower hearts were favoured the most. The high calorie food, means there is a lot of locked up energy inside the food (Hunter, 2003). As the pigeons were only able to burn this energy off within their enclosure, the results may vary if compared to pigeons which are released outside for exercise during the day Pigeons should consume a food that is slow energy released, such as barley (Janssens, Hesta, & Wilde, 2000).

Page 30 of 44

Experiment three could be improved by changing the routine of the feeds. The low calorie food could be fed for a whole week, once a day, and then the high calorie food could be fed for a whole week, and then a further week where they are mixed together. Lea, (1979), researched different foraging techniques in pigeons with a similar routine. The pigeons were fed once a day but for six days at a time for each foraging trial. This routine could help the pigeons understand the foods they are being given, which could create a new preference, especially if they are let outside for exercise to burn off energy as well.

4.3 Temperature

The data was collected from the 4th October 2012 until the 4 th November 2012. All three experiments involved the temperature being recorded before feeding at 8am and 4pm. For the first experiment the temperatures ranged no higher than 14 °C and no lower than 2 °C for the mornings. This data was put into a Spearman’s Correlation, which showed it was very nearly significant, (r s=0.214, p>0.05). With this result, the null hypothesis was rejected and the alternative was accepted as it showed racing pigeons do eat more when it’s warmer. It was thought that the pigeons would have eaten more when it was colder to keep themselves warm, however these results show different.

The temperatures recorded for experiment two, consisted of being put into a Pearson’s correlation, due to the data being parametric, which was revealed from a Kolmogorov- Smirnov Test. The Pearson’s correlation showed a significance, (r=0.474, p<0.001). This indicated that the null hypothesis was rejected and that the alternative could be accepted. These results also show that the pigeons ate more when it was warmer, even when the temperatures from this experiment ranged from 1 °C to 10 °C during the morning feeds, even though its colder temperatures compared to experiment one.

Experiment three also showed a significance from another Pearson’s correlation, (r=- 0.110, p>0.385). The null hypothesis was rejected and the alternative hypothesis was

Page 31 of 44

accepted again. The temperatures during this experiment ranged from -4°C to 6 °C during the morning feeds, which showed that even cold temperatures of -4°C, don’t encourage the pigeons to eat any more than they usually would.

Research has discovered that pigeons will wait a long period of time before they realise cold temperatures have occurred and they need to consume more food. Ostheim, (1992), had an experiment design, where the birds could influence the ambient temperature by breaking light beams. However considering they had this opportunity, it wasn’t until the body weight had reached approximately 70% of its initial value, that the bird then increased their feeding activity. This may suggest that the racing pigeon’s used for the three experiments, may have not thought it was cold enough yet, and if temperatures were to drop dramatically into the minus Celsius, they may have then increased their food intake to a lot more than they were eating in the temperatures ranging between 14 °C and 2 °C . The following three experiments could also be carried out in the summer; to see if that has a different preference to colour or food type.

The Bischof-Kohler hypothesis (Paxton & Hampton, 2009), states that, other animals are incapable of anticipating future needs and that any future oriented behaviours performed are either fixed action patterns or cued by their current motivational state. However it has been found from previous studies pigeons can solve tasks through training for future circumstances, but only over very short time scales (Raby, Alexis, Dickinson, & Clayton, 2007). Zentall & Singer, (2007), experimented with pigeons, training them to press certain keys in order to receive food. Once they had practised the pigeons had to remember to press the correct keys, otherwise they wouldn’t receive any food. All this research indicates that pigeons can set themselves up for change and survival. The temperature may only affect their feeding, if it increases or decreases rapidly, especially as the racing pigeons have to cope with climate changes through seasons, behavioural changes, breeding and moulting (Zalakevicius, 2000). The results gathered from the three experiments are unusual as it was predicted that the pigeons would eat more when cold, as previous research has shown that fasting

Page 32 of 44

can induce nocturnal hypothermia in pigeons (Rashotte, Pastukhov, Poliakov, & Henderson, 1998). However Briese, (1985), discussed how the body temperature of pigeons drops through the night, which may result in why the pigeons ate so much during the morning, regardless of the temperature.

Improvements that could be made for recording the temperature could include making several recordings through the day. If it was chosen to feed the pigeons at more intervals through the day, then the temperature could be recorded at each feeding time, to discover if the pigeons ate more at the warmest part of the day. However if food was only given once or twice a day, recordings could be made in-between times as well. Also the same methods could be carried out with temperature recordings done through the night at 8pm, 11pm, 2am, and 5am. This could then determine the prediction that if when the pigeon’s body temperature drops through the night, it encourages them to eat more the next morning (Briese, 1985).

4.4 General Discussion

As experiment two discovered that racing pigeons have a colour preference of red and natural, but a dislike to green, experiment three, (calorific foods), could be completed again, but colour the barley (least favoured), low calorie food, their preferred colour of red. This could lead to further research to see if pigeons will eat the high calorie food over the low calorie food, even when it’s dyed their preferred colour.

There have been many studies on pigeons to find if they can identify the differences between colour and food, from observing them daily or through training (Wanga, Jianga, & Frosta, 1993). Zentall, (2010), was a researcher that trained pigeons to a certain coloured stimuli, if the pigeons chose the correct colour they would be rewarded with food. On average it found that pigeons showed 69.3% preference for a certain stimuli during the training. This also reveals that pigeons do have a colour preference.

Page 33 of 44

It can be seen from this study that racing pigeons have a colour preference, which supports the aim of these experiments, which was to help pigeon racers, find a way to help pigeons consume all of their food so they have enough energy for racing. Pigeon racers could dye their food red, however further studies could be done to find other ways to encourage pigeon’s to eat all their food. Instead of using colours, flavours could be added to the feed.

Research has been done involving red-winged blackbirds (Agelaius phoeniceus) in captivity, to determine preferences for colours and food. The outcome revealed they preferred red food to blue food and preferred sweet flavours rather than bitter (Werner, Kimball, & Provenza, 2008). With this outline of birds preferring sweet or bitter, research could be done using flavours such as vanilla, ginger or banana that will give off odours (Dukas & Simpson, 2009). Colours can be common stimuli in signalling systems, but odours can be as well. Gamberale-stille, (2001), explains when young chicks are presented with an odour, it can change their behaviour quickly. This could lead to birds, pigeons comparing different food odours and preferring certain ones. As well as flavours, different scent could be used as well. This could involve basil, thyme or lavender, which could then lead to using aromatherapy in pigeons or birds. There is very little research for using aromatherapy in birds; however equipment has been designed, such as aromatherapy mats, which can be placed in dog beds, bird cages and cat’s beds, to prevent stress (Licciardo, 2001).

Racing pigeons have to fly long distances without stopping for water (Haase, Rees, & Harvey, 1986), so when they return home, pigeon racers should have food and water waiting for them inside the lofts. Further study could involve giving pigeons water whilst they eat the food in their individual boxes. The food can still be weighed as normal, but the water could be measured as well, to see how much they drank when eating. Food location in their boxes could also be experimented with, by moving the food pot around, to see if it consumed more food when the food pot is in a specific place. However previous research has shown that pigeons will eat the food that’s nearest to them (Willson & Comet, 1993).

Page 34 of 44

5. Conclusion

The aims of this study involved discovering if racing pigeons have a preference to their food, whether it be colour or calorific. The results from the study were proposed to help pigeon racers of today find a way to encourage the pigeons to eat all of their food before a race. As pigeons don’t land whilst racing, (Haase, Rees, & Harvey, 1986), they need enough energy to last the entire journey.

It was discovered that the pigeon’s had a preference for their foods being the colours red and natural, when given the choice of all five colours. This could be explained due to these colours being in pigeon corn regularly, however the results did show they least preferred green which was concluded in many other experiments, (Strasser & Bingman, 1999) and (Priel, 2007). Further research to distinguish that red and natural are the preferred colours, could be to give smaller quantities of food, more times through the day, as it was found pigeons like to identify foods, (McKenzie & Whittingham, 2010), so having smaller quantities will allow them to identify all the colours. Also adult birds could be used as the subjects as they will have experienced different coloured foods previously (Mora, Ross, Gorsevski, Chowdhury, & Bingman, 2012).

The third experiment consisting of calorific preference resulted in the pigeon’s preferring the high calorie food, sunflower hearts. As the pigeon nutritionally, should in take more of the low-calorie food, for a slow release of energy, as they were not getting a large amount of exercise in their daily routine, apart from in their enclosure, further research on this subject matter should be completed. This can be done using the same method but giving the pigeon’s daily exercise, (Janssens, Hesta, & Wilde, 2000). This would however need a larger sample size, due to risk of injury and predators when flying outside the lofts (Walcott, 1996).

Temperature resulted with an unexpected outcome, which could be explained due to their body temperature dropping at night; entailing them to eat more in the

Page 35 of 44

morning, regardless to what the temperature was (Briese, 1985). Further research would be needed to justify this more, this can be done by taking the temperature at set times through the night.

It is important that food preference of racing pigeon’s is studied further, in order to succeed in helping pigeon racers win the races, by the pigeon having all the sufficient nutritional energy it needs. It can lead to further information for pigeon flyers today and also by giving the pigeons the correct amount of food, it can look after their welfare within the sport of racing.

Page 36 of 44

6. References

Adebayo-Oyetoro, .. (2012). Production and quality evaluation of complementary food formulated from fermented sorghum, walnut and ginger. Journal of Applied Biosciences, 54 , 3901– 3910.

Alexander, D. J. (2011). Newcastle disease in the European Union 2000 to 2009. Avian Pathology, 40 (6), 547-558.

Bahrami, A. M. (2012, July 24). Pathological study of parasitism in racing pigeons: An indication of its effects on community health. African Journal of Biotechnology, 11 (59), 12364-12370.

Barta, Z., Liker, A., & Mónus, F. (2004). The effects of predation risk on the use of social foraging tactics. Animal Behaviour, 67 (2), 301–308.

Bauer, C. M., Glassman, L. W., Cyr, N. E., & Romero, L. M. (2011). Effects of predictable and unpredictable food restriction on the stress response in molting and non-molting European starlings (Sturnus vulgaris). Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 160 (3), 390–399.

Biedermann, T., & Garlick, D. (2012, September). Food choice in the laboratory pigeon. Behavioural Processes, 91 (1), 129–132.

Bordel, R., & Haase, E. (2000). Influence of flight on protein catabolism, especially myofilament breakdown, in homing pigeons. Journal of Comparative Physiology B, 170 (1), 51-58.

Borgia, G., & Keagy, J. (2006). An inverse relationship between decoration and food colour preferences in satin bowerbirds does not support the sensory drive hypothesis. Animal Behaviour, 72 , 1125-1133.

Brakstad, F., & Raaholt, M. H. (2009, 2 25). Food and Feed Supplement and its use. European Patent , 169-1626.

Briese, E. (1985). Rats prefer ambient temperatures out of phase with their body temperature circadian rhythm. Brain Research, 345 (2), 389–393.

Carrascal, L. M., Seoane, J., & Villén-Pérez, S. (2012). Temperature and food constraints in wintering birds — an experimental approach in montane Mediterranean oakwoods. Community Ecology, 13 (2), 221-229.

Clement, T. S., & Feltus, J. R. (2000, March). “work ethic” in pigeons: Reward value is directly related to the effort or time required to obtain the reward. Psychonomic Bulletin & Review , 7 (1), 100-106.

Coelho, S. (2010). Birds shun organic wheat. Planet Earth , 1-10.

Costantini, D. (2010). Effects of diet quality on serum oxidative status and body mass in male and female pigeons during reproduction. Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 156 (2), 294–299.

Page 37 of 44

Cousquer, G., & Parsons, D. (2007). Veterinary care of the racing pigeon. Journal of the British Veterinary Association, 29 (6), 344-355.

De Herdt, P., & Pasmans, F. (2009). 15 – Pigeons. Handbook of Avian Medicine (Second Edition) , 350– 376.

Dell'Ariccia, G., Dell'Omo, G., & Lipp, H.-P. (2009). The influence of experience in orientation: GPS tracking of homing pigeons released over the sea after directional training. The Journal of Experimental Biology, 212 , 178-183.

Diarra, S. S., Usman, B. A., Igwebuike, J. U., & Yisa, A. G. (2010). Breeding for efficient phytate- phosphorus utilization by poultry. International Journal of Poultry Science, 9 (10), 923-930.

Dittrich, L. (2009). Categorization of Photographs by Pigeons: Behavioural and Neurobiological Investigations. Neuroscience, 1 , 9-10.

Dittrich, L., Adam, R., Ünver, E., & Güntürkün, O. (2010). Pigeons identify individual humans but show no sign of recognizing them in photographs. Behavioural Processes, 83 (1), 82-89.

Dixon, A. (2002). Attacks by birds of prey on racing pigeons. . A report for the Confederation of Long Distance Racing Pigeon Unions of Great Britain and Northern Ireland. , 4-57.

Dukas, R., & Simpson, S. J. (2009). Locusts show rapid individual learning but no social learning about food. Animal Behaviour, 78 (2), 307–311.

Emmerton, J. (2001). Pigeons’ discrimination of color proportion in computer-generated visual displays. Animal Learning & Behavior, 29 (1), 21-35.

Flack, A., Pettit, B., Freeman, R., Guilford, T., & Biro, D. (2012). What are leaders made of? The role of individual experience in determining leader–follower relations in homing pigeons. Animal Behaviour, 83 (3), 703–709.

Friedrich, A. M., & Zentall, T. R. (2004). Pigeons shift their preference toward locations of food that take more effort to obtain. Behavioural Processes, 67 (3), 405-415.

Gamberale–Stille, G. (2001). Fruit or aposematic insect? Context-dependent colour preferences in domestic chicks. Proceedings of the Royal Society of London. Series B: Biological Sciences, 268 (1485), 2525-2529.

Garlick, D., Gant, D. J., Brakel, L. A., & Blaisdell, A. P. (2011). Attributional and Relational Processing in Pigeons. Frontiers in Psychology, 2 , 1.

Geiser, F. (2013). Hibernation. Current Biology, 23 (5), 188-193.

Green, L., Myerson, J., Holt, D. D., Slevin, J. R., & Estle, S. J. (2004). Discounting of delayed food rewards in pigeons and rats: is there a magnitude effect? Journal of the Experimental Analysis of Behavior, 81 (1), 39–50.

Page 38 of 44

Guilford, T., Åkesson, S., Gagliardo, A., & Holland, R. A. (2011). Migratory navigation in birds: new opportunities in an era of fast-developing tracking technology. The Journal of Experimental Biology, 214 , 3705-3712.

Haase, E., Rees, A., & Harvey, S. (1986). Flight stimulates adrenocortical activity in pigeons. General and comparative endocrinology, 61 (3), 424-427.

Hagstrum, J. (2000, April 1). Infrasound and the avian navigational map. The Journal of Experimental Biology, 203 , 1103-1111.

Hartley, L. (2000). Colour preferences and coloured bait consumption by weka Gallirallus australis, an endemic New Zealand rail. Biological Conservation, 93 (2), 255–263.

Hawkins, P. (2010). The Welfare Implications of Housing Captive Wild and Domesticated Birds. Animal Welfare, 9 , 53-102.

Henderson, D. (1992, September). Ingestive behavior and body temperature of pigeons during long- term cold exposure. Physiology & Behavior, 52 (3), 455–469.

Higgins, D. (2013, february 14). The premier organisation for pigeon racing in the UK . Retrieved February 14, 2013, from The Royal Pigeon Racing Association: http://www.rpra.org/

Honkavaara, J., Koivula, M., Korpimäki, E., Siitari, H., & Viitala, J. (2002). Ultraviolet vision and foraging in terrestrial vertebrates. Oikos, 98 (3), 505–511.

Humphreys, E. M., Carrington-Cotton, A., & Wernham, C. V. (2010). A review of an exploratory trial on Sparrowhawk attack rates at pigeon racing lofts in relation to some management practice. Biological and Environmental Sciences , 1-58.

Hunter, L. (2003). Thorsons Calorie Counter. London: HarperThorsons.

Janssens, G. P., Hesta, M., & Wilde, R. O. (2000). The effect of L-carnitine on body weight, body composition and nutrient intake in adult pigeons (Columba livia domestica). Archiv für Geflügelkunde, 64 (1), 29-33.

Johnes, M. (2007, September). Pigeon Racing and Working-class Culture in Britain, c. 1870-1950. Cultural and Social History, 4 (3), 361-383.

Joshua, G., & Ali, Z. (2011). Avian Diversity with the varing urban congestions of Lahore. The Journal of Animal and Plant Sciences, 21 (2), 421-428.

Kelly, R., & Grant, D. S. (2001). A differential outcomes effect using biologically neutral outcomes in delayed matching-to-sample with pigeons. The Quarterly Journal of Experimental Psychology Section B: Comparative and Physiological Psychology, 54 (1), 69-79.

Killeen, P. R., Cate, H., & Tran, T. (1993). Scaling pigeons' choice of feeds: bigger is better. Journal of Experimental Analysis of Behavior, 60 (1), 203–217.

Page 39 of 44

Kim, L. C., Garner, J. P., & Millam, J. R. (2009). Preferences of Orange-winged Amazon parrots (Amazona amazonica) for cage enrichment devices. Applied Animal Behaviour Science, 120 (3-4), 216-223.

Klemas, V. V. (2013). Remote sensing and navigation in the animal world: an overview. Sensor Review, 33 (1), 3-13.

Knight, K. (2011). Pigeons use right nostril to sniff way home. The Journal of Experimental Biology, 214 (4), 1-2.

Larrinaga, A. R. (2010). A univariate analysis of variance design for multiple-choice feeding- preference experiments: A hypothetical example with fruit-eating birds. Acta Oecologica, 36 (1), 141–148.

Laurila, M. (2005, July). The effect of ambient temperature and simulated predation risk on fasting- induced nocturnal hypothermia of pigeons in outdoor conditions. Journal of Thermal Biology, 30 (5), 392–399.

Lazareva, O. F. (2005, April 29). Object discrimination by pigeons: effects of object color and shape. Behavioural Processes, 69 (1), 17–31.

Lea, S. E. (1979). Foraging and reinforcement chedules in the pigeon: Optimal and non-optimal aspects of choice. Animal Behaviour, 27 , 875-886.

Leising, K. J., Garlick, D., Parenteau, M., & Blaisdell, A. P. (2009). Behavioral research in pigeons with ARENA: An Automated Remote Environmental Navigation Apparatus. Behavioural Processes, 81(1), 105–113.

Licciardo, R. (2001). Aromatherapy mats for pets. Patent and Trademark Office, 6 , 1-2.

LoBue, V. (2011, September). Pretty in pink: The early development of gender-stereotyped colour preferences. Developmental Psychology, 29 (3), 656–667.

Lubyk, D. M., & Spetch, M. L. (2012). Finding the best angle: pigeons (Columba livia) weight angular information more heavily than relative wall length in an open-field geometry task. Animal Cognition, 15 (3), 305-312.

Lydall, E. S. (2010, November). Rats place greater value on rewards produced by high effort: An animal analogue of the “effort justification” effect. Journal of Experimental Social Psychology, 46 (6), 1134–1137.

Maury, D. L., Mauch, R. J., Hammer, A. N., & Bingman, V. P. (2010). Spatial and feature-based memory representation in free-flying homing pigeons. Animal Cognition, 13 (5), 733-743.

Mazur, J. E. (2010, July). Animal Behaviour Processes. Experimental Psychology, 36 (3), 321-333.

McKenzie, A. J., & Whittingham, M. J. (2010). Birds select conventional over organic wheat when given free choice. Journal of the Science of Food and Agriculture, 90 (11), 1861-1869.

Page 40 of 44

McLean, R. G. (1972). Acceptance of Apholate-Treated Bait by Pigeons. American Midland Naturalist, 87 (2), 527-530.

Meade, J., Biro, D., & Guilford, T. (2006). Route recognition in the homing pigeon, Columba livia. Animal Behaviour, 72 (5), 975–980.

Mehlhorn, J., & Rehkämper, G. (2009). Neurobiology of the homing pigeon—a review. Naturwissenschaften, 96 (9), 1011-1025.

Mora, C. V., Davison, M., Wild, J. M., & Walker, M. M. (2004). Magnetoreception and its trigeminal mediation in the homing pigeon. Nature, 432 , 508-511.

Mora, C. V., Ross, J. D., Gorsevski, P. V., Chowdhury, B., & Bingman, V. P. (2012). Evidence for discrete landmark use by pigeons during homing. The Journal of Experimental Biology, 215 (19), 3379-3387.

Moran, S. (1999). Rejection of dyed field rodent baits by Feral Pigeons and Chukar Partridges. Phytoparasitica, 27 (1), 9-17.

Nagy, M., Ákos, Z., Biro, D., & Vicsek, T. (2010). Hierarchical group dynamics in pigeon flocks. Nature, 464 , 890-893.

Ostheim, J. (1992). Coping with food-limited conditions: Feeding behavior, temperature preference, and nocturnal hypothermia in pigeons. Physiology & Behavior, 51 (2), 353-361.

Paxton, R., & Hampton, R. R. (2009). Tests of planning and the Bischof-Köhler hypothesis in rhesus monkeys (Macaca mulatta). Behavioural processes, 80 (3), 238-246.

Pecchia, T., Gagliardo, A., & Vallortigara, G. (2011). Stable Panoramic Views Facilitate Snap-Shot Like Memories for Spatial Reorientation in Homing Pigeons. PLoS ONE, 6 (7), 1-6.

Pike, T. W. (2012). Generalised Chromaticity Diagrams for Animals with n-chromatic Colour Vision. Journal of Insect Behavior , 25 (3), 277-286.

Powers, L. V. (2002). DABVP (Avian) . Veterinary Care of Columbiformes , 540 , 1-4.

Priel, A. (2007). Broilers and layers respond differently to coloured light. World Poultry Science, 23 (4), 17.

Raby, C. R., Alexis, D. M., Dickinson, A., & Clayton, N. S. (2007). Planning for the future by western scrub-jays. Nature, 445 , 919-921.

Rashotte, M. E. (1997, January). Nocturnal digestion, cloacal excretion, and digestion-related thermogenesis in pigeons (Columba livia). Physiology & Behaviour, 61 (1), 83–92.

Rashotte, M. E., Pastukhov, I. F., Poliakov, E. L., & Henderson, R. P. (1998). Vigilance states and body temperature during the circadian cycle in fed and fasted pigeons (Columba livia). Comparative Physiology, 275 (5), 1690-1702.

Page 41 of 44

Reilly, M. P., Posadas-Sánchez, D., Kettle, L. C., & Killeen, P. R. (2012). Rats (Rattus norvegicus) and pigeons (Columbia livia) are sensitive to the distance to food, but only rats request more food when distance increases. Behavioural Processes, 91 (3), 236–243.

Roper, T. J. (1997). Colour preferences of domestic chicks in relation to food and water presentation. Applied Animal Behaviour Science, 54 (2-3), 207–213.

Rupiper, D. J. (1998). Diseases That Affect Race Performance of Homing Pigeons. Part I: Husbandry, Diagnostic Strategies, and Viral Diseases. Journal of Avian Medicine and Surgery, 12 (2), 70- 77.

Schmidt, V., & Schaefer, H. M. (2004). Unlearned preference for red may facilitate recognition of palatable food in young omnivorous birds. Evolutionary Ecology Research, 6 , 919-925.

Scullion, F. T., & Scullion, M. G. (2007). Pathologic Findings in Racing Pigeons (Columba livia domestica) With “Young Bird Sickness”. Journal of Avian Medicine and Surgery, 21 (1), 1-7.

Senar, J. C., Møller, A. P., Ruiz, I., Negro, J. J., Broggi, J., & Hohtola, E. (2010). Specific Appetite for Carotenoids in a Colorful Bird. PLoS ONE, 5 (5), 1-10.

Skelhorn, J. (2011). Colour biases are a question of conspecifics’ taste. Animal Behaviour, 81 (4), 825– 829.

Strasser, R., & Bingman, V. P. (1999). The effects of hippocampal lesions in homing pigeons on a one- trial food association task. Journal of Comparative Physiology A, 185 (6), 583-590.

Thalau, P., Holtkamp-Rötzler, E., Fleissner, G., & Wiltschko, W. (2007). Homing pigeons (Columba livia f. domestica) can use magnetic cues for locating food. Naturwissenschaften, 94 (10), 813-819.

Ulrich, C., & Prior, H. (1999). Left-hemispheric superiority for visuospatial orientation in homing pigeons. Behavioural Brain Research, 104 (1-2), 169–178.

Vriends, M. M. (2005). Pigeons. New York, USA: Barron's Educational Series, Inc.

Walcott, C. (1996). Pigeon homing: observations, experiments and confusions. The Journal of Experimental Biology, 199 (1), 21-27.

Walker, H. (1988). Fitness for anything – comparative aspects of fitness and training. Journal of the Royal Society of Medicine, 81 (11), 674–675.

Wanga, Y.-C., Jianga, S., & Frosta, B. J. (1993). Visual processing in pigeon nucleus rotundus: Luminance, color, motion, and looming subdivisions. Visual Neuroscience, 10 (1), 21-30.

Watanabe, S., & Masuda, S. (2010). Integration of auditory and visual information in human face discrimination in pigeons: Behavioral and anatomical study. Behavioural Brain Research, 207 (1), 61–69.

Weber, N. (2011). An Introduction to Pigeon Racing in the United States. Avian Veterinarians , 227.

Page 42 of 44

Werner, S. J., Kimball, B. A., & Provenza, F. D. (2008). Food color, flavor, and conditioned avoidance among red-winged blackbirds. Physiology & Behavior, 93 , 110-117.

Willson, M. F., & Comet, T. A. (1993). Food choices by northwestern crows: experiments with captive, free-ranging and hand-raised birds. Condor, 95 (3), 596-615.

Yahner, R. H. (2012). Migration, Orientation, and Navigation. Wildlife Behavior and Conservation , 145-150 .

Yong, S. A., Buddhamas, K., & Newman, A. E. (2011). Social rank, neophobia and observational learning in black-capped chickadees. Behaviour, 148 (1), 55-69.

Zalakevicius, M. (2000). Global Climate Change, Bird Migration and Bird Strike Problems. International Bird Strike Committee, 509 , 17-21.

Zentall, T. R. (2010, October). Justification of Effort by Humans and Pigeons. A Journal of the Association for Psychological Science, 19 (5), 296-300 .

Zentall, T. R. (2010). Justification of Effort by Humans and Pigeons Cognitive Dissonance or Contrast? Current Directions in Psychological Science, 19 (5), 296-300.

Zentall, T. R., & Singer, R. A. (2007, May). Within-Trial Contrast: When is a Failure to Replicate Not a Type I Error? Journal of the Experimental Analysis of Behaviour, 87 (3), 401–404.

Zimmerman, P. H. (2009). Involvement of the sun and the magnetic compass of domestic fowl in its spatial orientation. Applied Animal Behaviour Science, 116 (2-4), 204–210.

Page 43 of 44

7. Appendix

Page 44 of 44